Wearable display systems with nanowire led micro-displays

ABSTRACT

A wearable display system includes one or more nanowire LED micro-displays. The nanowire micro-LED displays may be monochrome or full-color. The nanowire LEDs forming the arrays may have an advantageously narrow angular emission profile and high light output. Where a plurality of nanowire LED micro-displays is utilized, the micro-displays may be positioned at different sides of an optical combiner, for example, an X-cube prism which receives light rays from different micro-displays and outputs the light rays from the same face of the cube. The optical combiner directs the light to projection optics, which outputs the light to an eyepiece that relays the light to a user&#39;s eye. The eyepiece may output the light to the user&#39;s eye with different amounts of wavefront divergence, to place virtual content on different depth planes.

PRIORITY CLAIM

This application claims priority to: U.S. Prov. Patent App. 63/005,132,entitled “WEARABLE DISPLAY SYSTEMS WITH NANOWIRE LED MICRO-DISPLAYS” andfiled on Apr. 3, 2020, which is incorporated herein by reference in itsentirety.

INCORPORATION BY REFERENCE

This application incorporates by reference the entirety of U.S.application Ser. No. 16/221,359, filed on Dec. 14, 2018; U.S.Provisional Application No. 62/786,199, filed Dec. 28, 2018; U.S.Provisional Application No. 62/702,707, filed on Jul. 24, 2018; and U.S.application Ser. No. 15/481,255, filed Apr. 6, 2017.

BACKGROUND Field

The present disclosure relates to display systems and, moreparticularly, to augmented and virtual reality display systems.

Description of the Related Art

Modern computing and display technologies have facilitated thedevelopment of systems for so called “virtual reality” or “augmentedreality” experiences, in which digitally reproduced images or portionsthereof are presented to a user in a manner wherein they seem to be, ormay be perceived as, real. A virtual reality, or “VR”, scenariotypically involves the presentation of digital or virtual imageinformation without transparency to other actual real-world visualinput; an augmented reality, or “AR”, scenario typically involvespresentation of digital or virtual image information as an augmentationto visualization of the actual world around the user. A mixed reality,or “MR”, scenario is a type of AR scenario and typically involvesvirtual objects that are integrated into, and responsive to, the naturalworld. For example, an MR scenario may include AR image content thatappears to be blocked by or is otherwise perceived to interact withobjects in the real world.

Referring to FIG. 1, an AR scene 10 is depicted. The user of an ARtechnology sees a real-world park-like setting 20 featuring people,trees, buildings in the background, and a concrete platform 30. The useralso perceives that he/she “sees” “virtual content” such as a robotstatue 40 standing upon the real-world platform 30, and a flyingcartoon-like avatar character 50 which seems to be a personification ofa bumble bee. These elements 50, 40 are “virtual” in that they do notexist in the real world. Because the human visual perception system iscomplex, it is challenging to produce AR technology that facilitates acomfortable, natural-feeling, rich presentation of virtual imageelements amongst other virtual or real-world imagery elements.

SUMMARY

In some embodiments, a head-mounted display system is provided. Thehead-mounted display system includes: a head-mountable frame; a nanowiremicro-LED display supported by the frame; and an eyepiece supported bythe frame. The nanowire LED micro-display is configured to output imagelight and the eyepiece is configured to receive the image light from thenanowire LED micro-display and to direct the image light to an eye of auser upon mounting the frame on the user.

In some other embodiments, a head-mounted display system is provided.The head-mounted display system includes: a waveguide assembly includingone or more waveguides; and an image projection system including anarray of nanowire micro-LEDs. The image projection system is configuredto project images onto the waveguide assembly. Each waveguide of thewaveguide assembly includes: an in-coupling optical element configuredto incouple light from the image projection system into the waveguide;and an out-coupling optical element configured to outcouple incoupledlight out of the waveguide. The waveguide assembly is configured tooutput the outcoupled light with variable amounts of wavefrontdivergence corresponding to a plurality of depth planes.

Additional examples of embodiments are enumerated below.

Example 1. A head-mounted display system comprising:

-   -   a head-mountable frame;    -   a nanowire micro-LED display supported by the frame, wherein the        nanowire LED micro-display is configured to output image light;        and    -   an eyepiece supported by the frame, wherein the eyepiece is        configured to receive the image light from the nanowire LED        micro-display and to direct the image light to an eye of a user        upon mounting the frame on the user.

Example 2. The head-mounted display system of Example 1, wherein thenanowire LED micro-display is one of a plurality of nanowire LEDmicro-displays,

-   -   further comprising an X-cube prism,    -   wherein each of the nanowire micro-LED displays faces a        different side of the X-cube prism,    -   wherein the eyepiece comprises an in-coupling optical element,        and    -   wherein an output side of the X-cube prism faces the light        in-coupling element.

Example 3. The head-mounted display system of Example 2, wherein thenanowire LED micro-displays are monochrome nanowire LED micro-displays.

Example 4. The head-mounted display system of Example 3, whereinreflective surfaces of the X-cube prism are configured to localize lightfrom different monochrome nanowire LED micro-displays onto differentareas of the eyepiece.

Example 5. The head-mounted display system of Example 4, wherein theeyepiece comprises a plurality of in-coupling optical elements having aspatial arrangement providing distinct light paths from the X-cube prismto the in-coupling optical elements, wherein a spatial arrangement ofthe areas corresponds to the spatial arrangement of the in-couplingoptical elements.

Example 6. The head-mounted display system of Example 1, wherein theeyepiece comprises a plurality of waveguides forming a waveguide stack,each waveguide of the waveguide stack comprising:

-   -   an in-coupling optical element configured to in-couple light        from the nanowire LED micro-display into the waveguide; and    -   an out-coupling optical element configured to out-couple        incoupled light out of the waveguide.

Example 7. The head-mounted display system of Example 6, wherein thewaveguide stack comprises a plurality of sets of waveguides, whereineach set of waveguides comprises a dedicated waveguide for a componentcolor.

Example 8. The head-mounted display system of Example 1, furthercomprising variable focus lens elements, wherein a waveguide comprisingdiffractive light in-coupling and out-coupling optical elements isbetween first and second variable focus lens elements, wherein the firstvariable focus lens element is configured to modify a wavefrontdivergence of light outputted by the waveguide, wherein the secondvariable focus lens element is configured to modify a wavefrontdivergence of light from an external world propagating through thesecond variable focus lens element.

Example 9. The head-mounted display system of Example 1, furthercomprising a color filter between two neighboring waveguides of awaveguide stack of the eyepiece, wherein a first of the neighboringwaveguides precedes a second of the neighboring waveguides in a lightpath extending from the micro-display, wherein the color filter isconfigured to selectively absorb light of a wavelength corresponding toa wavelength of light configured to be in-coupled by the in-couplingoptical element of the first of the neighboring waveguides.

Example 10. The head-mounted display system of Example 9, furthercomprising:

-   -   a third waveguide following the second of the neighboring        waveguides in the light path; and    -   an other color filter configured to selectively absorb light of        a wavelength corresponding to a wavelength of light configured        to be in-coupled by the in-coupling optical element of the        second of the neighboring waveguides.

Example 11. The head-mounted display system of Example 1, wherein thenanowire LED micro-display comprises spaced-apart arrays of monochromenanowire micro-LEDs on a common substrate backplane.

Example 12. The head-mounted display system of Example 11, wherein theeyepiece comprises a plurality of waveguides,

-   -   wherein the waveguides form a waveguide stack,    -   wherein each waveguide comprises in-coupling optical elements,    -   wherein, as seen in a top-down view, a spatial arrangement of        the in-coupling optical elements comprises different in-coupling        optical elements of different waveguides localized in different        spaced-apart positions,    -   wherein a spatial arrangement of the arrays of monochrome        nanowire micro-LEDs match a spatial arrangement of the        in-coupling optical elements.

Example 13. The head-mounted display system of Example 1, wherein thenanowire LED micro-display comprises an array of nanowire micro-LEDs,wherein some of the nanowire micro-LEDs are configured to emit light ofdifferent component colors than others of the array of nanowiremicro-LEDs.

Example 14. A head-mounted display system comprising:

-   -   a waveguide assembly comprising one or more waveguides; and    -   an image projection system comprising an array of nanowire        micro-LEDs, the image projection system configured to project        images onto the waveguide assembly,    -   wherein each waveguide of the waveguide assembly comprises:        -   an in-coupling optical element configured to incouple light            from the image projection system into the waveguide; and        -   an out-coupling optical element configured to outcouple            incoupled light out of the waveguide,        -   wherein the waveguide assembly is configured to output the            outcoupled light with variable amounts of wavefront            divergence corresponding to a plurality of depth planes.

Example 15. The head-mounted display system of Example 14, wherein thenanowire micro-LEDs each have an angular emission profile of less than50°.

Example 16. The head-mounted display system of Example 15, wherein theangular emission profile is 30-45°.

Example 17. The head-mounted display system of Example 14, furthercomprising projection optics configured to converge light from thenanowire LED micro-display onto the in-coupling optical elements of theone or more waveguides.

Example 18. The head-mounted display system of Example 14, whereinindividual ones of the light emitters are configured to emit light ofone of a plurality of component colors,

-   -   wherein the waveguide assembly comprises a plurality of sets of        waveguides,    -   wherein each set of waveguides comprises a dedicated waveguide        for each component color, wherein each set of waveguides        comprises out-coupling optical elements configured to output        light with wavefront divergence corresponding to a common depth        plane, wherein different sets of waveguides output light with        different amounts of wavefront divergence corresponding to        different depth planes.

Example 19. The head-mounted display system of Example 14, furthercomprising variable focus lens elements, wherein the waveguide assemblyis between first and second variable focus lens elements, wherein thefirst variable focus lens element is configured to modify a wavefrontdivergence of light outputted by the waveguide assembly, wherein thesecond variable focus lens element is configured to modify a wavefrontdivergence of light from an external world to the second variable focuslens element.

Example 20. The head-mounted display of Example 14, wherein thewaveguide assembly comprises a stack of waveguides.

Example 21. The head-mounted display system of Claim 14, furthercomprising absorptive color filters on major surfaces of at least someof the waveguides, wherein the absorptive color filters on majorsurfaces of the waveguides are configured to absorb light of wavelengthsin-coupled into a corresponding waveguide, wherein the waveguides arearranged in a stack.

Example 22. The head-mounted display system of Claim 14, wherein thewaveguide assembly comprises a stack of waveguides, wherein thein-coupling optical elements are configured to in-couple light with thein-coupled light propagating generally in a propagation directionthrough an associated waveguide, wherein the in-coupling opticalelements occupy an area having a width parallel to the propagationdirection and a length along an axis crossing the propagation direction,wherein the length is greater than the width.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a user's view of augmented reality (AR) through an ARdevice.

FIG. 2 illustrates a conventional display system for simulatingthree-dimensional imagery for a user.

FIGS. 3A-3C illustrate relationships between radius of curvature andfocal radius.

FIG. 4A illustrates a representation of the accommodation-vergenceresponse of the human visual system.

FIG. 4B illustrates examples of different accommodative states andvergence states of a pair of eyes of the user.

FIG. 4C illustrates an example of a representation of a top-down view ofa user viewing content via a display system.

FIG. 4D illustrates another example of a representation of a top-downview of a user viewing content via a display system.

FIG. 5 illustrates aspects of an approach for simulatingthree-dimensional imagery by modifying wavefront divergence.

FIG. 6 illustrates an example of a waveguide stack for outputting imageinformation to a user.

FIG. 7 illustrates an example of exit beams outputted by a waveguide.

FIG. 8 illustrates an example of a stacked eyepiece in which each depthplane includes images formed using multiple different component colors.

FIG. 9A illustrates a cross-sectional side view of an example of a setof stacked waveguides that each includes an in-coupling optical element.

FIG. 9B illustrates a perspective view of an example of the plurality ofstacked waveguides of FIG. 9A.

FIG. 9C illustrates a top-down plan view of an example of the pluralityof stacked waveguides of FIGS. 9A and 9B.

FIG. 9D illustrates a top-down plan view of another example of aplurality of stacked waveguides.

FIG. 9E illustrates a top-down plan view of another example of aconfiguration for in-coupling optical elements.

FIG. 9F illustrates an example of a wearable display system.

FIG. 10 illustrates an example of a wearable display system with a lightprojection system having a spatial light modulator and a separate lightsource.

FIG. 11A illustrates an example of a wearable display system with alight projection system having multiple nanowire LED micro-displays.

FIG. 11B illustrates a top-down plan view of an example of a nanowireLED micro-display with an array of light emitters.

FIG. 11C illustrates a cross-sectional side view of an example of thenanowire LED micro-display of FIG. 11B formed of a nanowire LED array.

FIG. 12 illustrates another example of a wearable display system with alight projection system having multiple nanowire LED micro-displays andassociated light redirecting structures.

FIG. 13A illustrates an example of a side-view of a wearable displaysystem with a light projection system having multiple nanowire LEDmicro-displays and an eyepiece having waveguides with overlapping andlaterally-shifted light in-coupling optical elements.

FIG. 13B illustrates another example of a wearable display system with alight projection system having multiple nanowire LED micro-displaysconfigured to direct light to a single light in-coupling area of aneyepiece.

FIG. 14 illustrates an example of a wearable display system with asingle nanowire LED micro-display.

FIG. 15 illustrates a side view of an example of an eyepiece having astack of waveguides with overlapping in-coupling optical elements.

FIG. 16 illustrates a side view of an example of a stack of waveguideswith color filters for mitigating ghosting or crosstalk betweenwaveguides.

FIG. 17 illustrates an example of a top-down view of the eyepieces ofFIGS. 15 and 16.

FIG. 18 illustrates another example of a top-down view of the eyepiecesof FIGS. 15 and 16.

FIG. 19A illustrates a side view of an example of an eyepiece having astack of waveguides with overlapping and laterally-shifted in-couplingoptical elements.

FIG. 19B illustrates a side view of an example of the eyepiece of FIG.19A with color filters for mitigating ghosting or crosstalk betweenwaveguides.

FIG. 20A illustrates an example of a top-down view of the eyepieces ofFIGS. 19A and 19B.

FIG. 20B illustrates another example of a top-down view of the eyepiecesof FIGS. 19A and 19B.

FIG. 21 illustrates a side view of an example of re-bounce in awaveguide.

FIGS. 22A-22C illustrate examples of top-down views of an eyepiecehaving in-coupling optical elements configured to reduce re-bounce.

FIGS. 23A-23C illustrate additional examples of top-down views of aneyepiece having in-coupling optical elements configured to reducere-bounce.

FIG. 24A illustrates an example of angular emission profiles of lightemitted by individual light emitters of a nanowire LED micro-display,and light captured by projection optics.

FIG. 24B illustrates an example of the narrowing of angular emissionprofiles using an array of light collimators.

FIG. 25A illustrates an example of a side view of an array of taperedreflective wells for directing light to projection optics.

FIG. 25B illustrates an example of a side view of an asymmetric taperedreflective well.

FIGS. 26A-26C illustrate examples of differences in light paths forlight emitters at different positions relative to center lines ofoverlying lens.

FIG. 27 illustrates an example of a side view of individual lightemitters of a nanowire LED micro-display with an overlying nano-lensarray.

FIG. 28 is a perspective view of an example of the nanowire LEDmicro-display of FIG. 27.

FIG. 29 illustrates an example of a wearable display system with thefull-color nanowire LED micro-display of FIG. 28.

FIG. 30A illustrates an example of a wearable display system with ananowire LED micro-display and an associated array of light collimators.

FIG. 30B illustrates an example of a light projection system withmultiple nanowire LED micro-displays, each with an associated array oflight collimators.

FIG. 30C illustrates an example of a wearable display system withmultiple nanowire LED micro-displays, each with an associated array oflight collimators.

FIGS. 31A and 31B illustrate examples of waveguide assemblies havingvariable focus elements for varying the wavefront divergence of light toa viewer.

FIG. 32A illustrates an example of a wearable display system having alight projection system that directs light of different component colorsto an eyepiece without using an optical combiner to combine light ofdifferent colors.

FIG. 32B illustrates another example of a wearable display system havinga light projection system that directs light of different componentcolors to an eyepiece without using an optical combiner to combine thelight of different colors.

DETAILED DESCRIPTION

Augmented reality (AR) or virtual reality (VR) systems may displayvirtual content to a user, or viewer. This content may be displayed on ahead-mounted display, for example, as part of eyewear, that projectsimage information to the user's eyes. In addition, where the system isan AR system, the display may also transmit light from a surroundingenvironment to the user's eyes, to allow a view of the surroundingenvironment. As used herein, it will be appreciated that a“head-mounted” or “head mountable” display is a display that may bemounted on the head of the user or viewer.

Many head-mounted display systems utilize transmissive or reflectivespatial light modulators to form images that are presented to the user.A light source emits light, which is directed to the spatial lightmodulator, which then modulates the light, which is then directed to theuser. Lens structures may be provided between the light source and thespatial light modulator to focus light from the light source onto thespatial light modulator. Undesirably, the light source and relatedoptics may add bulkiness and weight to the display system. Thisbulkiness or weight may adversely impact the comfort of the head-mounteddisplay system and the ability to wear the head-mounted display systemfor long durations.

In addition, the frame rate limitations of some head-mounted displaysystems may cause viewing discomfort. Some head-mounted display systemsuse spatial light modulators to form images. Many spatial lightmodulators utilize movement of optical elements to modulate theintensity of light outputted by the spatial light modulator, to therebyform the images. For example, MEMS-based spatial light modulators mayutilize moving mirrors to modulate incident light, while LCoS-baseddisplays may utilize the movement of liquid crystal molecules tomodulate light. Other AR or VR systems may utilize scanning-fiberdisplays, in which the end of an optical fiber physically moves acrossan area while outputting light. The light outputted by the optical fiberis timed with the position of the end of the fiber, thereby effectivelymimicking pixels at different locations, and thereby forming images. Therequirement that the optical fibers, mirrors, and liquid crystalmolecules physically move limits the speed at which individual pixelsmay change states and also constrains the frame rate of displays usingthese optical elements.

Such limitations may cause viewing discomfort due to, for example,motion blur and/or mismatches between the orientation of the user's headand the displayed image. For example, there may be latency in thedetection of the orientation of the user's head and the presentation ofimages consistent with that orientation. In the timespan betweendetecting the orientation and presenting an image to the user, theuser's head may have moved. The presented image, however, may correspondto a view of an object from a different orientation. Such a mismatchbetween the orientation of the user's head and the presented image maycause discomfort in the user (for example, nausea).

In addition, scanning-fiber displays may present other undesirableoptical artifacts due to, for example, the small cross-section of thefibers, which requires the use of a high-intensity light source to formimages of desirable apparent brightness. Suitable high-intensity lightsources include lasers, which output coherent light. Undesirably, theuse of coherent light may cause optical artifacts.

Micro-LED displays have been proposed as replacements for theabove-noted spatial light modulators and scanning-fiber displays.Micro-LED displays have various advantages for use in head-mounteddisplay systems. As an example, micro-LED displays are emissive. Thepower consumption of emissive micro-displays generally varies with imagecontent, such that dim or sparse content requires less power to display.Since AR environments may often be sparse—since it may generally bedesirable for the user to be able to see their surroundingenvironment—emissive micro-displays may have an average powerconsumption below that of other display technologies that use a spatiallight modulator to modulate light from a light source. In contrast,other display technologies may utilize substantial power even for dim,sparse, or “all off”, virtual content. As another example, emissivemicro-displays may offer an exceptionally high frame-rate (which mayenable the use of a partial-resolution array) and may provide low levelsof visually apparent motion artifacts (for example, motion blur). Asanother example, emissive micro-displays may not require polarizationoptics of the type required by LCoS displays. Thus, emissivemicro-displays may avoid the optical losses present in polarizationoptics.

Many micro-LED displays include planar light emitters formed on asubstrate. Notably, the light emitters may have a Lambertian lightemission profile, and may emit light over the surface area of the lightemitter. Such micro-LED displays may have drawbacks in someconfigurations. For example, in some cases, optics may be utilized tonarrow the light emission profile, to allow more of the emitted light tobe directed to a user and thereby provide a higher energy efficiency.Such optics may add to the complexity and expense of a display systemutilizing the micro-LED displays. In addition, because of manufacturingand electrical considerations, decreases in the sizes of the lightemitters may be constrained, and reductions in light emitter size (andrelated increases in pixel density and resolution) may be challenging.For example, some microLED-based micro-displays may allow for a pixelpitch of about 2 to about 3 micron. Even at such pixel pitches, toprovide a desired number of pixels, the microLED display may still beundesirably large for use in a wearable display system, particularlysince a goal for such systems may be to have a form factor and sizesimilar to that of eyeglasses. In addition, the brightness of the lightemitters may be limited by their ability to withstand high currentdensities.

Various embodiments described herein utilize nanowire LEDmicro-displays, which may provide the advantages of micro-LED displaysgenerally, while providing further advantages for one or more of lightdirectionality, brightness, high scalability for increases in pixeldensity, improved color accuracy (for example, by providing high levelsof red light), and high manufacturing throughput. For example, nanowiremicro-LED displays may maintain electrical-to-light conversionefficiencies down to micron-size pixels, an advantage over planarmicro-LED designs in which efficiency may drop rapidly below, forexample, 10-20 microns. As a result, highly-efficient and exceptionallyhigh resolution nanowire LED arrays may be formed. Further, nanowireLEDs may offer built-in emission profile directionality and steering,which may be selected based on the physical design and composition ofthe nanowire LEDs. This can simplify the system architecture andmanufacture of the display systems utilizing the nanowire LEDs, sinceadditional optics for directionality and steering may be avoided.Moreover, in some embodiments, by omitting additional optics fordirectionality and steering, a nanowire LED array may be populated withnanowire LEDs without the constraint of designing and grouping nanowiresto interface with the additional optics. As a result, higher nanowiredensity and, thus, light output may be achieved without changing thesize of the micro-display. The use of a micro-display having nanowiremicro-LED arrays enables highly compact form factor viewing opticsassemblies (VOAs) for AR and VR wearable display systems. In someembodiments, the VOA's may include the nanowire LED micro-display and aneyepiece for relaying light from the micro-LED display to a user's eyes.Advantageously, such display systems may deliver high brightness in apower efficient manner, with high image quality metrics and coloruniformity over a wide field of view.

It will be appreciated that nano-wire LEDs may be formed of arrays ofvertically extending nanowires (for example, spaced-apart pillars ofmaterial) electrically connected to two electrodes. The nanowires emitlight upon application of current through the nanowires. In someembodiments, the nanowires may be considered to be diodes with P and Nportions.

The nanowires may also be considered to be three-dimensional LED deviceswith larger light emitting surface areas than typical planar LEDs. Forexample, a 1 μm×1 μm planar LED has a 1 μm² active emitter area, but, asan example, a group of 25 nanowires grown in the same 1 μm² footprint,each 1 μm tall and 100 nm diameter, may have a total active area of25×(π×0.1×1)=8 μm², which is eight times the light-emitting area of theplanar LED. This increase in the surface area to volume ratio for theLED “pixel” may enhance the light output of the nanowire LED. Thisenhancement may allow nanowire LED pixels to maintain high-brightnessoutput, even for very fine pixel pitch operation. In some embodiments,the properties of the emitted light (wavelength, external quantumefficiency, directionality) may also be tailored by choice of nanowireparameters, such as, but not limited to, material and dopant,dimensions, geometry, structure, refractive indices, etc. For example,the geometric shapes, sizes, and spacing of the nanowires may beselected to provide a light emission profile with a desireddirectionality.

In addition, the nanowires may be grouped together, to form pixels. Forexample, common contacts or electrodes may be used for one or morenanowires to form a pixel, or a discrete light emitter. Because eachnanowire may have a diameter of, for example, 100 nm to a few hundrednanometers, the pixel size and pitch may be determined by the size ofthe common electrodes for each group of nanowires. For example, thenanowires may be grouped into pixels defined by electrical contactsshared by the N and P portions of the group of nanowire diodes. Thus,the pixel size and pitch may be made exceptionally small, based on thesize of the electrodes. As a result, pixels of micron or sub-micronpitch may be achieved. In some embodiments, the pixel pitch is 2 μm orless, 1 μm or less, or 800 nm or less. In some embodiments, the pixelpitch may be in the range of 200 nm to 2 μm, 200 nm to 1 μm, or 200-800nm. As described herein, pixel pitch may refer to a distance betweensimilar points on directly adjacent light emitters along a particularaxis (for example, lateral axis), with different axes having their ownpixel pitch. For example, in some embodiments, the light emitters may beplaced more closely along a first axis than along a second axis (forexample, an orthogonal axis).

In addition, various physical properties of the nanowire LEDs mayadvantageously provide exceptional light-emitting properties. Forexample, the nanowire LEDs may be formed with low misfit dislocationsand may withstand higher current density values than planar LEDs,thereby permitting higher levels of light output. In addition, it willbe appreciated that nanowire LEDs emitting red light may be formed byheavy Indium doping of Ga nanowires. However, such doping may causecrystal lattice mismatches that decrease the light-emitting efficiencyof such nanowire LEDs. Because the nanowires may be sparsely distributedacross a substrate, low levels of accumulated crystal lattice mismatch(for example, mismatches between InN and GaN-based portions ofnanowires) may occur, which may have advantages for forming red LEDs.The low levels of lattice mismatches provide LEDs with high light-outputefficiency. As a result, high levels of red light output may beachieved, which may have advantages for forming displays with high coloraccuracy.

In addition, the nanowire LEDs may be formed using semiconductormanufacturing processes to form the nanowires and related electrodes,with, for example, Indium-doping utilized to provide the desiredelectronic bandgap tuning for the desired color of light output.Moreover, formation of the nanowire LEDs on a semiconductor substrateallows for process compatibility with CMOS backplanes (for example, viawafer-to-wafer bonding or flip-chip bonding). It will be appreciatedthat semiconductor manufacturing processes may provide high-throughputin high-yield manufacturing results.

In some embodiments, one or more nanowire LED micro-displays may beutilized to form images for a head-mounted display system. The lightcontaining the image information for forming these images may bereferred to as image light. It will be appreciated that image light mayvary in, for example, wavelength, intensity, polarization, etc. Thenanowire LED micro-displays output image light towards an eyepiece,which then relays the light to an eye of the user.

In some embodiments, one or more nanowire LED micro-displays may beutilized and positioned at different sides of an optical combiner, forexample, an X-cube prism or dichroic X-cube. The X-cube prism receiveslight rays from different micro-displays on different faces of the cubeand outputs the light rays from the different micro-displays out ofanother face of the cube. Light rays from all of the differentmicro-displays may be outputted from the same output face of the cube.The outputted light may be directed towards projection optics, which isconfigured to converge or focus the image light onto the eyepiece.

In some embodiments, the one or more nanowire LED micro-displays includemonochrome micro-displays, which are configured to output light of asingle component color. Combining various component colors forms a fullcolor image. In some embodiments, one or more of the nanowire LEDmicro-displays may have sub-pixels configured to emit light of two ormore, but not all, component colors utilized by the display system. Forexample, a single nanowire LED micro-display may have sub-pixels whichemit light of the colors blue and green, while a separate nanowire LEDmicro-display on a different face of the X-cube may have pixelsconfigured to emit red light. In some embodiments, the one or moremicro-displays are each full-color displays including, for example,pixels formed of multiple sub-pixels configured to emit light ofdifferent component colors. Advantageously, combining the light ofmultiple full-color micro-displays may increase display brightness anddynamic range.

It will be appreciated that the nanowire LED micro-displays may includearrays of light emitters. Preferably, as discussed herein, thecompositions and geometric shapes, sizes, and spacing of the nanowiresforming the nanowire LEDs are selected to provide a desired lightemission profile having a desired angular expanse.

Nevertheless, in some embodiments, the nanowire LEDs may emit light witha larger than desired angular emission profile. Undesirably, such anangular emission profile may “waste” light, since only a small portionof the emitted light may ultimately be incident on the eyepiece. In someembodiments, light collimators may be utilized to narrow the angularemission profile of light emitted by the nanowire LED light emitter. Asused herein, a light collimator is an optical structure which narrowsthe angular emission profile of incident light; that is, the lightcollimator receives light from an associated light emitter with arelatively wide initial angular emission profile and outputs that lightwith a narrower angular emission profile than the wide initial angularemission profile. In some embodiments, the rays of light exiting thelight collimator are more parallel than the rays of light received bythe light collimator, before being transmitted through and exiting thecollimator. Examples of light collimators include micro-lenses,nano-lenses, reflective wells, metasurfaces, and liquid crystalgratings. In some embodiments, the light collimators may be configuredto steer light to ultimately converge on different laterally-shiftedlight-coupling optical elements. In some embodiments, each light emitterhas a dedicated light collimator. The light collimators are preferablypositioned directly adjacent or contacting the light emitters, tocapture a large proportion of the light emitted by the associated lightemitters.

In some embodiments, a single nanowire LED micro-display may be utilizedto output light to the eyepiece. For example, the single nanowire LEDmicro-display may be a full-color display including light emitters thatemit light of different component colors. In some embodiments, the lightemitters may form groups, which are localized in a common area, witheach group including light emitters which emit light of each componentcolor. In such embodiments, each group of light emitters may share acommon micro-lens. Advantageously, light of different colors fromdifferent light emitters take a different path through the micro-lens,which may be manifested in light of different component colors beingincident on different in-coupling optical elements of an eyepiece, asdiscussed herein.

In some embodiments, the full-color micro-display may include repeatinggroups of light emitters of the same component color. For instance, themicro-display may include rows of light emitters, with the lightemitters of each individual row configured to emit light of the samecolor. Thus, different rows may emit light of different componentcolors. In addition, the micro-display may have an associated array oflight collimators configured to direct light to a desired location on aneyepiece, for example, to an associated in-coupling optical element.Advantageously, while the individual light emitters of such a full-colormicro-display may not be positioned to form a high-quality full-colorimage, as viewed directly on the micro-display, the lens arrayappropriately steers the light from the light emitters to the eyepiece,which combines monochrome images formed by light emitters of differentcolors, thereby forming a high-quality full-color image.

In some embodiments, the eyepiece receiving image light from thenanowire LED micro-displays may include a waveguide assembly. The areaof a waveguide of the waveguide assembly on which the image light isincident may include in-coupling optical elements which in-coupleincident image light, such that the light propagates through thewaveguide by total internal reflection (TIR). In some embodiments, thewaveguide assembly may include a stack of waveguides, each of which hasan associated in-coupling optical element. Different in-coupling opticalelements may be configured to in-couple light of different colors, suchthat different waveguides may be configured to propagate light ofdifferent colors therein. The waveguides may include out-couplingoptical elements, which out-couple light propagating therein, such thatthe out-coupled light propagates towards the eye of the user. In someembodiments, the waveguide assembly may include a single waveguidehaving an associated in-coupling optical element configured to in-couplelight of multiple different component colors.

In some embodiments, the in-coupling optical elements are laterallyshifted, as seen from the projection optics. Different in-couplingoptical elements may be configured to in-couple light of differentcolors. Preferably, image light of different colors take different pathsto the eyepiece and, thus, impinge upon different correspondingin-coupling optical elements.

In some embodiments, other types of eyepieces or optics for relayingimage light to the eyes of the user may be utilized. For example, asdiscussed herein, the eyepiece may include one or more waveguides whichpropagates image light therein by TIR. As another example, the eyepiecemay include a birdbath combiner including a semi-transparent mirror thatboth directs image light to a viewer and allows a view of the ambientenvironment.

In some embodiments, the eyepiece may be configured to selectivelyoutput light with different amounts of wavefront divergence, to providevirtual content at one or more virtual depth planes (also referred tosimply as “depth planes” herein) perceived to be at different distancesaway from the user. For example, the eyepiece may include one or morewaveguides each having out-coupling optical elements with differentoptical power to output light with different amounts of wavefrontdivergence. In some embodiments, a variable focus element may beprovided between the eyepiece and the user's eye. The variable focuselement may be configured to dynamically change optical power to providethe desired wavefront divergence for particular virtual content. In someembodiments, as an alternative to, or in addition to waveguide opticalstructures for providing optical power, the display systems may alsoinclude one or more lenses that provide or additionally provide opticalpowers.

Reference will now be made to the drawings, in which like referencenumerals refer to like parts throughout. Unless indicated otherwise, thedrawings are schematic and not necessarily drawn to scale.

FIG. 2 illustrates a conventional display system for simulatingthree-dimensional imagery for a user. It will be appreciated that auser's eyes are spaced apart and that, when looking at a real object inspace, each eye will have a slightly different view of the object andmay form an image of the object at different locations on the retina ofeach eye. This may be referred to as binocular disparity and may beutilized by the human visual system to provide a perception of depth.Conventional display systems simulate binocular disparity by presentingtwo distinct images 190, 200 with slightly different views of the samevirtual object—one for each eye 210, 220—corresponding to the views ofthe virtual object that would be seen by each eye were the virtualobject a real object at a desired depth. These images provide binocularcues that the user's visual system may interpret to derive a perceptionof depth.

With continued reference to FIG. 2, the images 190, 200 are spaced fromthe eyes 210, 220 by a distance 230 on a z-axis. The z-axis is parallelto the optical axis of the viewer with their eyes fixated on an objectat optical infinity directly ahead of the viewer. The images 190, 200are flat and at a fixed distance from the eyes 210, 220. Based on theslightly different views of a virtual object in the images presented tothe eyes 210, 220, respectively, the eyes may naturally rotate such thatan image of the object falls on corresponding points on the retinas ofeach of the eyes, to maintain single binocular vision. This rotation maycause the lines of sight of each of the eyes 210, 220 to converge onto apoint in space at which the virtual object is perceived to be present.As a result, providing three-dimensional imagery conventionally involvesproviding binocular cues that may manipulate the vergence of the user'seyes 210, 220, and that the human visual system interprets to provide aperception of depth.

Generating a realistic and comfortable perception of depth ischallenging, however. It will be appreciated that light from objects atdifferent distances from the eyes have wavefronts with different amountsof divergence. FIGS. 3A-3C illustrate relationships between distance andthe divergence of light rays. The distance between the object and theeye 210 is represented by, in order of decreasing distance, R1, R2, andR3. As shown in FIGS. 3A-3C, the light rays become more divergent asdistance to the object decreases. Conversely, as distance increases, thelight rays become more collimated. Stated another way, it may be saidthat the light field produced by a point (the object or a part of theobject) has a spherical wavefront curvature, which is a function of howfar away the point is from the eye of the user. The curvature increaseswith decreasing distance between the object and the eye 210. While onlya single eye 210 is illustrated for clarity of illustration in FIGS.3A-3C and other figures herein, the discussions regarding eye 210 may beapplied to both eyes 210 and 220 of a viewer.

With continued reference to FIGS. 3A-3C, light from an object that theviewer's eyes are fixated on may have different degrees of wavefrontdivergence. Due to the different amounts of wavefront divergence, thelight may be focused differently by the lens of the eye, which in turnmay require the lens to assume different shapes to form a focused imageon the retina of the eye. Where a focused image is not formed on theretina, the resulting retinal blur acts as a cue to accommodation thatcauses a change in the shape of the lens of the eye until a focusedimage is formed on the retina. For example, the cue to accommodation maytrigger the ciliary muscles surrounding the lens of the eye to relax orcontract, thereby modulating the force applied to the suspensoryligaments holding the lens, thus causing the shape of the lens of theeye to change until retinal blur of an object of fixation is eliminatedor minimized, thereby forming a focused image of the object of fixationon the retina (for example, fovea) of the eye. The process by which thelens of the eye changes shape may be referred to as accommodation, andthe shape of the lens of the eye required to form a focused image of theobject of fixation on the retina (for example, fovea) of the eye may bereferred to as an accommodative state.

With reference now to FIG. 4A, a representation of theaccommodation-vergence response of the human visual system isillustrated. The movement of the eyes to fixate on an object causes theeyes to receive light from the object, with the light forming an imageon each of the retinas of the eyes. The presence of retinal blur in theimage formed on the retina may provide a cue to accommodation, and therelative locations of the image on the retinas may provide a cue tovergence. The cue to accommodation causes accommodation to occur,resulting in the lenses of the eyes each assuming a particularaccommodative state that forms a focused image of the object on theretina (for example, fovea) of the eye. On the other hand, the cue tovergence causes vergence movements (rotation of the eyes) to occur suchthat the images formed on each retina of each eye are at correspondingretinal points that maintain single binocular vision. In thesepositions, the eyes may be said to have assumed a particular vergencestate. With continued reference to FIG. 4A, accommodation may beunderstood to be the process by which the eye achieves a particularaccommodative state, and vergence may be understood to be the process bywhich the eye achieves a particular vergence state. As indicated in FIG.4A, the accommodative and vergence states of the eyes may change if theuser fixates on another object. For example, the accommodated state maychange if the user fixates on a new object at a different depth on thez-axis.

Without being limited by theory, it is believed that viewers of anobject may perceive the object as being “three-dimensional” due to acombination of vergence and accommodation. As noted above, vergencemovements (for example, rotation of the eyes so that the pupils movetoward or away from each other to converge the lines of sight of theeyes to fixate upon an object) of the two eyes relative to each otherare closely associated with accommodation of the lenses of the eyes.Under normal conditions, changing the shapes of the lenses of the eyesto change focus from one object to another object at a differentdistance will automatically cause a matching change in vergence to thesame distance, under a relationship known as the “accommodation-vergencereflex.” Likewise, a change in vergence will trigger a matching changein lens shape under normal conditions.

With reference now to FIG. 4B, examples of different accommodative andvergence states of the eyes are illustrated. The pair of eyes 222 a isfixated on an object at optical infinity, while the pair eyes 222 b arefixated on an object 221 at less than optical infinity. Notably, thevergence states of each pair of eyes is different, with the pair of eyes222 a directed straight ahead, while the pair of eyes 222 converge onthe object 221. The accommodative states of the eyes forming each pairof eyes 222 a and 222 b are also different, as represented by thedifferent shapes of the lenses 210 a, 220 a.

Undesirably, many users of conventional “3-D” display systems find suchconventional systems to be uncomfortable or may not perceive a sense ofdepth at all due to a mismatch between accommodative and vergence statesin these displays. As noted above, many stereoscopic or “3-D” displaysystems display a scene by providing slightly different images to eacheye. Such systems are uncomfortable for many viewers, since they, amongother things, simply provide different presentations of a scene andcause changes in the vergence states of the eyes, but without acorresponding change in the accommodative states of those eyes. Rather,the images are shown by a display at a fixed distance from the eyes,such that the eyes view all the image information at a singleaccommodative state. Such an arrangement works against the“accommodation-vergence reflex” by causing changes in the vergence statewithout a matching change in the accommodative state. This mismatch isbelieved to cause viewer discomfort. Display systems that provide abetter match between accommodation and vergence may form more realisticand comfortable simulations of three-dimensional imagery.

Without being limited by theory, it is believed that the human eyetypically may interpret a finite number of depth planes to provide depthperception. Consequently, a highly believable simulation of perceiveddepth may be achieved by providing, to the eye, different presentationsof an image corresponding to each of these limited numbers of depthplanes. In some embodiments, the different presentations may provideboth cues to vergence and matching cues to accommodation, therebyproviding physiologically correct accommodation-vergence matching.

With continued reference to FIG. 4B, two depth planes 240, correspondingto different distances in space from the eyes 210, 220, are illustrated.For a given depth plane 240, vergence cues may be provided by thedisplaying of images of appropriately different perspectives for eacheye 210, 220. In addition, for a given depth plane 240, light formingthe images provided to each eye 210, 220 may have a wavefront divergencecorresponding to a light field produced by a point at the distance ofthat depth plane 240.

In the illustrated embodiment, the distance, along the z-axis, of thedepth plane 240 containing the point 221 is 1 m. As used herein,distances or depths along the z-axis may be measured with a zero-pointlocated at the exit pupils of the user's eyes. Thus, a depth plane 240located at a depth of 1 m corresponds to a distance of 1 m away from theexit pupils of the user's eyes, on the optical axis of those eyes withthe eyes directed towards optical infinity. As an approximation, thedepth or distance along the z-axis may be measured from the display infront of the user's eyes (for example, from the surface of a waveguide),plus a value for the distance between the device and the exit pupils ofthe user's eyes. That value may be called the eye relief and correspondsto the distance between the exit pupil of the user's eye and the displayworn by the user in front of the eye. In practice, the value for the eyerelief may be a normalized value used generally for all viewers. Forexample, the eye relief may be assumed to be 20 mm and a depth planethat is at a depth of 1 m may be at a distance of 980 mm in front of thedisplay.

With reference now to FIGS. 4C and 4D, examples of matchedaccommodation-vergence distances and mismatched accommodation-vergencedistances are illustrated, respectively. As illustrated in FIG. 4C, thedisplay system may provide images of a virtual object to each eye 210,220. The images may cause the eyes 210, 220 to assume a vergence statein which the eyes converge on a point 15 on a depth plane 240. Inaddition, the images may be formed by a light having a wavefrontcurvature corresponding to real objects at that depth plane 240. As aresult, the eyes 210, 220 assume an accommodative state in which theimages are in focus on the retinas of those eyes. Thus, the user mayperceive the virtual object as being at the point 15 on the depth plane240.

It will be appreciated that each of the accommodative and vergencestates of the eyes 210, 220 are associated with a particular distance onthe z-axis. For example, an object at a particular distance from theeyes 210, 220 causes those eyes to assume particular accommodativestates based upon the distances of the object. The distance associatedwith a particular accommodative state may be referred to as theaccommodation distance, A_(d). Similarly, there are particular vergencedistances, V_(d), associated with the eyes in particular vergencestates, or positions relative to one another. Where the accommodationdistance and the vergence distance match, the relationship betweenaccommodation and vergence may be said to be physiologically correct.This is considered to be the most comfortable scenario for a viewer.

In stereoscopic displays, however, the accommodation distance and thevergence distance may not always match. For example, as illustrated inFIG. 4D, images displayed to the eyes 210, 220 may be displayed withwavefront divergence corresponding to depth plane 240, and the eyes 210,220 may assume a particular accommodative state in which the points 15a, 15 b on that depth plane are in focus. However, the images displayedto the eyes 210, 220 may provide cues for vergence that cause the eyes210, 220 to converge on a point 15 that is not located on the depthplane 240. As a result, the accommodation distance corresponds to thedistance from the exit pupils of the eyes 210, 220 to the depth plane240, while the vergence distance corresponds to the larger distance fromthe exit pupils of the eyes 210, 220 to the point 15, in someembodiments. The accommodation distance is different from the vergencedistance. Consequently, there is an accommodation-vergence mismatch.Such a mismatch is considered undesirable and may cause discomfort inthe user. It will be appreciated that the mismatch corresponds todistance (for example, V_(d)-A_(d)) and may be characterized usingdiopters.

In some embodiments, it will be appreciated that a reference point otherthan exit pupils of the eyes 210, 220 may be utilized for determiningdistance for determining accommodation-vergence mismatch, so long as thesame reference point is utilized for the accommodation distance and thevergence distance. For example, the distances could be measured from thecornea to the depth plane, from the retina to the depth plane, from theeyepiece (for example, a waveguide of the display device) to the depthplane, and so on.

Without being limited by theory, it is believed that users may stillperceive accommodation-vergence mismatches of up to about 0.25 diopter,up to about 0.33 diopter, and up to about 0.5 diopter as beingphysiologically correct, without the mismatch itself causing significantdiscomfort. In some embodiments, display systems disclosed herein (forexample, the display system 250, FIG. 6) present images to the viewerhaving accommodation-vergence mismatch of about 0.5 diopter or less. Insome other embodiments, the accommodation-vergence mismatch of theimages provided by the display system is about 0.33 diopter or less. Inyet other embodiments, the accommodation-vergence mismatch of the imagesprovided by the display system is about 0.25 diopter or less, includingabout 0.1 diopter or less.

FIG. 5 illustrates aspects of an approach for simulatingthree-dimensional imagery by modifying wavefront divergence. The displaysystem includes a waveguide 270 that is configured to receive light 770that is encoded with image information, and to output that light to theuser's eye 210. The waveguide 270 may output the light 650 with adefined amount of wavefront divergence corresponding to the wavefrontdivergence of a light field produced by a point on a desired depth plane240. In some embodiments, the same amount of wavefront divergence isprovided for all objects presented on that depth plane. In addition, itwill be illustrated that the other eye of the user may be provided withimage information from a similar waveguide.

In some embodiments, a single waveguide may be configured to outputlight with a set amount of wavefront divergence corresponding to asingle or limited number of depth planes and/or the waveguide may beconfigured to output light of a limited range of wavelengths.Consequently, in some embodiments, a plurality or stack of waveguidesmay be utilized to provide different amounts of wavefront divergence fordifferent depth planes and/or to output light of different ranges ofwavelengths. As used herein, it will be appreciated at a depth plane maybe planar or may follow the contours of a curved surface.

FIG. 6 illustrates an example of a waveguide stack for outputting imageinformation to a user. A display system 250 includes a stack ofwaveguides, or stacked waveguide assembly, 260 that may be utilized toprovide three-dimensional perception to the eye/brain using a pluralityof waveguides 270, 280, 290, 300, 310. It will be appreciated that thedisplay system 250 may be considered a light field display in someembodiments. In addition, the waveguide assembly 260 may also bereferred to as an eyepiece.

In some embodiments, the display system 250 may be configured to providesubstantially continuous cues to vergence and multiple discrete cues toaccommodation. The cues to vergence may be provided by displayingdifferent images to each of the eyes of the user, and the cues toaccommodation may be provided by outputting the light that forms theimages with selectable discrete amounts of wavefront divergence. Statedanother way, the display system 250 may be configured to output lightwith variable levels of wavefront divergence. In some embodiments, eachdiscrete level of wavefront divergence corresponds to a particular depthplane and may be provided by a particular one of the waveguides 270,280, 290, 300, 310.

With continued reference to FIG. 6, the waveguide assembly 260 may alsoinclude a plurality of features 320, 330, 340, 350 between thewaveguides. In some embodiments, the features 320, 330, 340, 350 may beone or more lenses. The waveguides 270, 280, 290, 300, 310 and/or theplurality of lenses 320, 330, 340, 350 may be configured to send imageinformation to the eye with various levels of wavefront curvature orlight ray divergence. Each waveguide level may be associated with aparticular depth plane and may be configured to output image informationcorresponding to that depth plane. Image injection devices 360, 370,380, 390, 400 may function as a source of light for the waveguides andmay be utilized to inject image information into the waveguides 270,280, 290, 300, 310, each of which may be configured, as describedherein, to distribute incoming light across each respective waveguide,for output toward the eye 210. Light exits an output surface 410, 420,430, 440, 450 of the image injection devices 360, 370, 380, 390, 400 andis injected into a corresponding input surface 460, 470, 480, 490, 500of the waveguides 270, 280, 290, 300, 310. In some embodiments, each ofthe input surfaces 460, 470, 480, 490, 500 may be an edge of acorresponding waveguide, or may be part of a major surface of thecorresponding waveguide (that is, one of the waveguide surfaces directlyfacing the world 510 or the viewer's eye 210). In some embodiments, asingle beam of light (for example a collimated beam) may be injectedinto each waveguide to output an entire field of cloned collimated beamsthat are directed toward the eye 210 at particular angles (and amountsof divergence) corresponding to the depth plane associated with aparticular waveguide. In some embodiments, a single one of the imageinjection devices 360, 370, 380, 390, 400 may be associated with andinject light into a plurality (for example, three) of the waveguides270, 280, 290, 300, 310.

In some embodiments, the image injection devices 360, 370, 380, 390, 400are discrete displays that each produce image information for injectioninto a corresponding waveguide 270, 280, 290, 300, 310, respectively. Insome other embodiments, the image injection devices 360, 370, 380, 390,400 are the output ends of a single multiplexed display which may, forexample, pipe image information via one or more optical conduits (suchas fiber optic cables) to each of the image injection devices 360, 370,380, 390, 400. It will be appreciated that the image informationprovided by the image injection devices 360, 370, 380, 390, 400 mayinclude light of different wavelengths, or colors (for example,different component colors, as discussed herein).

In some embodiments, the light injected into the waveguides 270, 280,290, 300, 310 is provided by a light projection system 520, whichincludes a light module 530, which may include a light emitter, such asa light emitting diode (LED). The light from the light module 530 may bedirected to and modified by a light modulator 540, for example, aspatial light modulator, via a beam splitter 550. The light modulator540 may be configured to change the perceived intensity of the lightinjected into the waveguides 270, 280, 290, 300, 310 to encode the lightwith image information. Examples of spatial light modulators includeliquid crystal displays (LCD) including a liquid crystal on silicon(LCOS) displays. It will be appreciated that the image injection devices360, 370, 380, 390, 400 are illustrated schematically and, in someembodiments, these image injection devices may represent different lightpaths and locations in a common projection system configured to outputlight into associated ones of the waveguides 270, 280, 290, 300, 310. Insome embodiments, the waveguides of the waveguide assembly 260 mayfunction as ideal lens while relaying light injected into the waveguidesout to the user's eyes. In this conception, the object may be thespatial light modulator 540 and the image may be the image on the depthplane.

In some embodiments, the display system 250 may be a scanning fiberdisplay including one or more scanning fibers configured to projectlight in various patterns (for example, raster scan, spiral scan,Lissajous patterns, etc.) into one or more waveguides 270, 280, 290,300, 310 and ultimately to the eye 210 of the viewer. In someembodiments, the illustrated image injection devices 360, 370, 380, 390,400 may schematically represent a single scanning fiber or a bundle ofscanning fibers configured to inject light into one or a plurality ofthe waveguides 270, 280, 290, 300, 310. In some other embodiments, theillustrated image injection devices 360, 370, 380, 390, 400 mayschematically represent a plurality of scanning fibers or a plurality ofbundles of scanning fibers, each of which are configured to inject lightinto an associated one of the waveguides 270, 280, 290, 300, 310. Itwill be appreciated that one or more optical fibers may be configured totransmit light from the light module 530 to the one or more waveguides270, 280, 290, 300, 310. It will be appreciated that one or moreintervening optical structures may be provided between the scanningfiber, or fibers, and the one or more waveguides 270, 280, 290, 300, 310to, for example, redirect light exiting the scanning fiber into the oneor more waveguides 270, 280, 290, 300, 310.

A controller 560 controls the operation of one or more of the stackedwaveguide assembly 260, including operation of the image injectiondevices 360, 370, 380, 390, 400, the light source 530, and the lightmodulator 540. In some embodiments, the controller 560 is part of thelocal data processing module 140. The controller 560 includesprogramming (for example, instructions in a non-transitory medium) thatregulates the timing and provision of image information to thewaveguides 270, 280, 290, 300, 310 according to, for example, any of thevarious schemes disclosed herein. In some embodiments, the controllermay be a single integral device, or a distributed system connected bywired or wireless communication channels. The controller 560 may be partof the processing modules 140 or 150 (FIG. 9F) in some embodiments.

With continued reference to FIG. 6, the waveguides 270, 280, 290, 300,310 may be configured to propagate light within each respectivewaveguide by total internal reflection (TIR). The waveguides 270, 280,290, 300, 310 may each be planar or have another shape (for example,curved), with major top and bottom surfaces and edges extending betweenthose major top and bottom surfaces. In the illustrated configuration,the waveguides 270, 280, 290, 300, 310 may each include out-couplingoptical elements 570, 580, 590, 600, 610 that are configured to extractlight out of a waveguide by redirecting the light, propagating withineach respective waveguide, out of the waveguide to output imageinformation to the eye 210. Extracted light may also be referred to asout-coupled light and the out-coupling optical elements light may alsobe referred to light extracting optical elements. An extracted beam oflight may be outputted by the waveguide at locations at which the lightpropagating in the waveguide strikes a light extracting optical element.The out-coupling optical elements 570, 580, 590, 600, 610 may, forexample, be gratings, including diffractive optical features, asdiscussed further herein. While illustrated disposed at the bottom majorsurfaces of the waveguides 270, 280, 290, 300, 310, for ease ofdescription and drawing clarity, in some embodiments, the out-couplingoptical elements 570, 580, 590, 600, 610 may be disposed at the topand/or bottom major surfaces, and/or may be disposed directly in thevolume of the waveguides 270, 280, 290, 300, 310, as discussed furtherherein. In some embodiments, the out-coupling optical elements 570, 580,590, 600, 610 may be formed in a layer of material that is attached to atransparent substrate to form the waveguides 270, 280, 290, 300, 310. Insome other embodiments, the waveguides 270, 280, 290, 300, 310 may be amonolithic piece of material and the out-coupling optical elements 570,580, 590, 600, 610 may be formed on a surface and/or in the interior ofthat piece of material.

With continued reference to FIG. 6, as discussed herein, each waveguide270, 280, 290, 300, 310 is configured to output light to form an imagecorresponding to a particular depth plane. For example, the waveguide270 nearest the eye may be configured to deliver collimated light (whichwas injected into such waveguide 270), to the eye 210. The collimatedlight may be representative of the optical infinity focal plane. Thenext waveguide up 280 may be configured to send out collimated lightwhich passes through the first lens 350 (for example, a negative lens)before it may reach the eye 210; such first lens 350 may be configuredto create a slight convex wavefront curvature so that the eye/braininterprets light coming from that next waveguide up 280 as coming from afirst focal plane closer inward toward the eye 210 from opticalinfinity. Similarly, the third up waveguide 290 passes its output lightthrough both the first 350 and second 340 lenses before reaching the eye210; the combined optical power of the first 350 and second 340 lensesmay be configured to create another incremental amount of wavefrontcurvature so that the eye/brain interprets light coming from the thirdwaveguide 290 as coming from a second focal plane that is even closerinward toward the person from optical infinity than was light from thenext waveguide up 280.

The other waveguide layers 300, 310 and lenses 330, 320 are similarlyconfigured, with the highest waveguide 310 in the stack sending itsoutput through all of the lenses between it and the eye for an aggregatefocal power representative of the closest focal plane to the person. Tocompensate for the stack of lenses 320, 330, 340, 350 whenviewing/interpreting light coming from the world 510 on the other sideof the stacked waveguide assembly 260, a compensating lens layer 620 maybe disposed at the top of the stack to compensate for the aggregatepower of the lens stack 320, 330, 340, 350 below. Such a configurationprovides as many perceived focal planes as there are availablewaveguide/lens pairings. Both the out-coupling optical elements of thewaveguides and the focusing aspects of the lenses may be static (i.e.,not dynamic or electro-active). In some alternative embodiments, eitheror both may be dynamic using electro-active features.

In some embodiments, two or more of the waveguides 270, 280, 290, 300,310 may have the same associated depth plane. For example, multiplewaveguides 270, 280, 290, 300, 310 may be configured to output imagesset to the same depth plane, or multiple subsets of the waveguides 270,280, 290, 300, 310 may be configured to output images set to the sameplurality of depth planes, with one set for each depth plane. This mayprovide advantages for forming a tiled image to provide an expandedfield of view at those depth planes.

With continued reference to FIG. 6, the out-coupling optical elements570, 580, 590, 600, 610 may be configured to both redirect light out oftheir respective waveguides and to output this light with theappropriate amount of divergence or collimation for a particular depthplane associated with the waveguide. As a result, waveguides havingdifferent associated depth planes may have different configurations ofout-coupling optical elements 570, 580, 590, 600, 610, which outputlight with a different amount of divergence depending on the associateddepth plane. In some embodiments, the light extracting optical elements570, 580, 590, 600, 610 may be volumetric or surface features, which maybe configured to output light at specific angles. For example, the lightextracting optical elements 570, 580, 590, 600, 610 may be volumeholograms, surface holograms, and/or diffraction gratings. In someembodiments, the features 320, 330, 340, 350 may not be lenses; rather,they may simply be spacers (for example, cladding layers and/orstructures for forming air gaps).

In some embodiments, the out-coupling optical elements 570, 580, 590,600, 610 are diffractive features that form a diffraction pattern, or“diffractive optical element” (also referred to herein as a “DOE”).Preferably, the DOE's have a sufficiently low diffraction efficiency sothat only a portion of the light of the beam is deflected away towardthe eye 210 with each intersection of the DOE, while the rest continuesto move through a waveguide via TIR. The light carrying the imageinformation is thus divided into a number of related exit beams thatexit the waveguide at a multiplicity of locations and the result is afairly uniform pattern of exit emission toward the eye 210 for thisparticular collimated beam bouncing around within a waveguide.

In some embodiments, one or more DOEs may be switchable between “on”states in which they actively diffract, and “off” states in which theydo not significantly diffract. For instance, a switchable DOE mayinclude a layer of polymer dispersed liquid crystal, in whichmicrodroplets include a diffraction pattern in a host medium, and therefractive index of the microdroplets may be switched to substantiallymatch the refractive index of the host material (in which case thepattern does not appreciably diffract incident light) or themicrodroplet may be switched to an index that does not match that of thehost medium (in which case the pattern actively diffracts incidentlight).

In some embodiments, a camera assembly 630 (for example, a digitalcamera, including visible light and infrared light cameras) may beprovided to capture images of the eye 210 and/or tissue around the eye210 to, for example, detect user inputs and/or to monitor thephysiological state of the user. As used herein, a camera may be anyimage capture device. In some embodiments, the camera assembly 630 mayinclude an image capture device and a light source to project light (forexample, infrared light) to the eye, which may then be reflected by theeye and detected by the image capture device. In some embodiments, thecamera assembly 630 may be attached to the frame or support structure 80(FIG. 9F) and may be in electrical communication with the processingmodules 140 and/or 150, which may process image information from thecamera assembly 630. In some embodiments, one camera assembly 630 may beutilized for each eye, to separately monitor each eye.

With reference now to FIG. 7, an example of exit beams outputted by awaveguide is shown. One waveguide is illustrated, but it will beappreciated that other waveguides in the waveguide assembly 260 (FIG. 6)may function similarly, where the waveguide assembly 260 includesmultiple waveguides. Light 640 is injected into the waveguide 270 at theinput surface 460 of the waveguide 270 and propagates within thewaveguide 270 by TIR. At points where the light 640 impinges on the DOE570, a portion of the light exits the waveguide as exit beams 650. Theexit beams 650 are illustrated as substantially parallel but, asdiscussed herein, they may also be redirected to propagate to the eye210 at an angle (for example, forming divergent exit beams), dependingon the depth plane associated with the waveguide 270. It will beappreciated that substantially parallel exit beams may be indicative ofa waveguide with out-coupling optical elements that out-couple light toform images that appear to be set on a depth plane at a large distance(for example, optical infinity) from the eye 210. Other waveguides orother sets of out-coupling optical elements may output an exit beampattern that is more divergent, which would require the eye 210 toaccommodate to a closer distance to bring it into focus on the retinaand would be interpreted by the brain as light from a distance closer tothe eye 210 than optical infinity.

In some embodiments, a full color image may be formed at each depthplane by overlaying images in each of the component colors, for example,three or more component colors. FIG. 8 illustrates an example of astacked waveguide assembly in which each depth plane includes imagesformed using multiple different component colors. The illustratedembodiment shows depth planes 240 a-240 f, although more or fewer depthsare also contemplated. Each depth plane may have three or more componentcolor images associated with it, including: a first image of a firstcolor, G; a second image of a second color, R; and a third image of athird color, B. Different depth planes are indicated in the figure bydifferent numbers for diopters (dpt) following the letters G, R, and B.Just as examples, the numbers following each of these letters indicatediopters (1/m), or inverse distance of the depth plane from a viewer,and each box in the figures represents an individual component colorimage. In some embodiments, to account for differences in the eye'sfocusing of light of different wavelengths, the exact placement of thedepth planes for different component colors may vary. For example,different component color images for a given depth plane may be placedon depth planes corresponding to different distances from the user. Suchan arrangement may increase visual acuity and user comfort and/or maydecrease chromatic aberrations.

In some embodiments, light of each component color may be outputted by asingle dedicated waveguide and, consequently, each depth plane may havemultiple waveguides associated with it. In such embodiments, each box inthe figures including the letters G, R, or B may be understood torepresent an individual waveguide, and three waveguides may be providedper depth plane where three component color images are provided perdepth plane. While the waveguides associated with each depth plane areshown adjacent to one another in this drawing for ease of description,it will be appreciated that, in a physical device, the waveguides mayall be arranged in a stack with one waveguide per level. In some otherembodiments, multiple component colors may be outputted by the samewaveguide, such that, for example, only a single waveguide may beprovided per depth plane.

With continued reference to FIG. 8, in some embodiments, G is the colorgreen, R is the color red, and B is the color blue. In some otherembodiments, other colors associated with other wavelengths of light,including magenta and cyan, may be used in addition to or may replaceone or more of red, green, or blue.

It will be appreciated that references to a given color of lightthroughout this disclosure will be understood to encompass light of oneor more wavelengths within a range of wavelengths of light that areperceived by a viewer as being of that given color. For example, redlight may include light of one or more wavelengths in the range of about620-780 nm, green light may include light of one or more wavelengths inthe range of about 492-577 nm, and blue light may include light of oneor more wavelengths in the range of about 435-493 nm.

In some embodiments, the light source 530 (FIG. 6) may be configured toemit light of one or more wavelengths outside the visual perceptionrange of the viewer, for example, infrared and/or ultravioletwavelengths. In addition, the in-coupling, out-coupling, and other lightredirecting structures of the waveguides of the display 250 may beconfigured to direct and emit this light out of the display towards theuser's eye 210, for example, for imaging and/or user stimulationapplications.

With reference now to FIG. 9A, in some embodiments, light impinging on awaveguide may need to be redirected to in-couple that light into thewaveguide. An in-coupling optical element may be used to redirect andin-couple the light into its corresponding waveguide. FIG. 9Aillustrates a cross-sectional side view of an example of a plurality orset 660 of stacked waveguides that each includes an in-coupling opticalelement. The waveguides may each be configured to output light of one ormore different wavelengths, or one or more different ranges ofwavelengths. It will be appreciated that the stack 660 may correspond tothe stack 260 (FIG. 6) and the illustrated waveguides of the stack 660may correspond to part of the plurality of waveguides 270, 280, 290,300, 310, except that light from one or more of the image injectiondevices 360, 370, 380, 390, 400 is injected into the waveguides from aposition that requires light to be redirected for in-coupling.

The illustrated set 660 of stacked waveguides includes waveguides 670,680, and 690. Each waveguide includes an associated in-coupling opticalelement (which may also be referred to as a light input area on thewaveguide), with, for example, in-coupling optical element 700 disposedon a major surface (for example, an upper major surface) of waveguide670, in-coupling optical element 710 disposed on a major surface (forexample, an upper major surface) of waveguide 680, and in-couplingoptical element 720 disposed on a major surface (for example, an uppermajor surface) of waveguide 690. In some embodiments, one or more of thein-coupling optical elements 700, 710, 720 may be disposed on the bottommajor surface of the respective waveguide 670, 680, 690 (particularlywhere the one or more in-coupling optical elements are reflective,deflecting optical elements). As illustrated, the in-coupling opticalelements 700, 710, 720 may be disposed on the upper major surface oftheir respective waveguide 670, 680, 690 (or the top of the next lowerwaveguide), particularly where those in-coupling optical elements aretransmissive, deflecting optical elements. In some embodiments, thein-coupling optical elements 700, 710, 720 may be disposed in the bodyof the respective waveguide 670, 680, 690. In some embodiments, asdiscussed herein, the in-coupling optical elements 700, 710, 720 arewavelength selective, such that they selectively redirect one or morewavelengths of light, while transmitting other wavelengths of light.While illustrated on one side or corner of their respective waveguide670, 680, 690, it will be appreciated that the in-coupling opticalelements 700, 710, 720 may be disposed in other areas of theirrespective waveguide 670, 680, 690 in some embodiments.

As illustrated, the in-coupling optical elements 700, 710, 720 may belaterally offset from one another, as seen in the illustrated head-onview in a direction of light propagating to these in-coupling opticalelements. In some embodiments, each in-coupling optical element may beoffset such that it receives light without that light passing throughanother in-coupling optical element. For example, each in-couplingoptical element 700, 710, 720 may be configured to receive light from adifferent image injection device 360, 370, 380, 390, and 400 as shown inFIG. 6, and may be separated (for example, laterally spaced apart) fromother in-coupling optical elements 700, 710, 720 such that itsubstantially does not receive light from the other ones of thein-coupling optical elements 700, 710, 720.

Each waveguide also includes associated light distributing elements,with, for example, light distributing elements 730 disposed on a majorsurface (for example, a top major surface) of waveguide 670, lightdistributing elements 740 disposed on a major surface (for example, atop major surface) of waveguide 680, and light distributing elements 750disposed on a major surface (for example, a top major surface) ofwaveguide 690. In some other embodiments, the light distributingelements 730, 740, 750, may be disposed on a bottom major surface ofassociated waveguides 670, 680, 690, respectively. In some otherembodiments, the light distributing elements 730, 740, 750, may bedisposed on both top and bottom major surface of associated waveguides670, 680, 690, respectively; or the light distributing elements 730,740, 750, may be disposed on different ones of the top and bottom majorsurfaces in different associated waveguides 670, 680, 690, respectively.

The waveguides 670, 680, 690 may be spaced apart and separated by, forexample, gas, liquid, and/or solid layers of material. For example, asillustrated, layer 760 a may separate waveguides 670 and 680; and layer760 b may separate waveguides 680 and 690. In some embodiments, thelayers 760 a and 760 b are formed of low refractive index materials(that is, materials having a lower refractive index than the materialforming the immediately adjacent one of waveguides 670, 680, 690).Preferably, the refractive index of the material forming the layers 760a, 760 b is 0.05 or more, or 0.10 or less than the refractive index ofthe material forming the waveguides 670, 680, 690. Advantageously, thelower refractive index layers 760 a, 760 b may function as claddinglayers that facilitate total internal reflection (TIR) of light throughthe waveguides 670, 680, 690 (for example, TIR between the top andbottom major surfaces of each waveguide). In some embodiments, thelayers 760 a, 760 b are formed of air. While not illustrated, it will beappreciated that the top and bottom of the illustrated set 660 ofwaveguides may include immediately neighboring cladding layers.

Preferably, for ease of manufacturing and other considerations, thematerial forming the waveguides 670, 680, 690 are similar or the same,and the material forming the layers 760 a, 760 b are similar or thesame. In some embodiments, the material forming the waveguides 670, 680,690 may be different between one or more waveguides, and/or the materialforming the layers 760 a, 760 b may be different, while still holding tothe various refractive index relationships noted above.

With continued reference to FIG. 9A, light rays 770, 780, 790 areincident on the set 660 of waveguides. It will be appreciated that thelight rays 770, 780, 790 may be injected into the waveguides 670, 680,690 by one or more image injection devices 360, 370, 380, 390, 400 (FIG.6).

In some embodiments, the light rays 770, 780, 790 have differentproperties, for example, different wavelengths or different ranges ofwavelengths, which may correspond to different colors. The in-couplingoptical elements 700, 710, 720 each deflect the incident light such thatthe light propagates through a respective one of the waveguides 670,680, 690 by TIR. In some embodiments, the in-coupling optical elements700, 710, 720 each selectively deflect one or more particularwavelengths of light, while transmitting other wavelengths to anunderlying waveguide and associated in-coupling optical element.

For example, in-coupling optical element 700 may be configured todeflect ray 770, which has a first wavelength or range of wavelengths,while transmitting rays 780 and 790, which have different second andthird wavelengths or ranges of wavelengths, respectively. Thetransmitted ray 780 impinges on and is deflected by the in-couplingoptical element 710, which is configured to deflect light of a secondwavelength or range of wavelengths. The ray 790 is deflected by thein-coupling optical element 720, which is configured to selectivelydeflect light of third wavelength or range of wavelengths.

With continued reference to FIG. 9A, the deflected light rays 770, 780,790 are deflected so that they propagate through a correspondingwaveguide 670, 680, 690; that is, the in-coupling optical elements 700,710, 720 of each waveguide deflects light into that correspondingwaveguide 670, 680, 690 to in-couple light into that correspondingwaveguide. The light rays 770, 780, 790 are deflected at angles thatcause the light to propagate through the respective waveguide 670, 680,690 by TIR. The light rays 770, 780, 790 propagate through therespective waveguide 670, 680, 690 by TIR until impinging on thewaveguide's corresponding light distributing elements 730, 740, 750.

With reference now to FIG. 9B, a perspective view of an example of theplurality of stacked waveguides of FIG. 9A is illustrated. As notedabove, the in-coupled light rays 770, 780, 790, are deflected by thein-coupling optical elements 700, 710, 720, respectively, and thenpropagate by TIR within the waveguides 670, 680, 690, respectively. Thelight rays 770, 780, 790 then impinge on the light distributing elements730, 740, 750, respectively. The light distributing elements 730, 740,750 deflect the light rays 770, 780, 790 so that they propagate towardsthe out-coupling optical elements 800, 810, 820, respectively.

In some embodiments, the light distributing elements 730, 740, 750 areorthogonal pupil expanders (OPE's). In some embodiments, the OPE'sdeflect or distribute light to the out-coupling optical elements 800,810, 820 and, in some embodiments, may also increase the beam or spotsize of this light as it propagates to the out-coupling opticalelements. In some embodiments, the light distributing elements 730, 740,750 may be omitted and the in-coupling optical elements 700, 710, 720may be configured to deflect light directly to the out-coupling opticalelements 800, 810, 820. For example, with reference to FIG. 9A, thelight distributing elements 730, 740, 750 may be replaced without-coupling optical elements 800, 810, 820, respectively. In someembodiments, the out-coupling optical elements 800, 810, 820 are exitpupils (EP's) or exit pupil expanders (EPE's) that direct light in aviewer's eye 210 (FIG. 7). It will be appreciated that the OPE's may beconfigured to increase the dimensions of the eye box in at least oneaxis and the EPE's may be to increase the eye box in an axis crossing,for example, orthogonal to, the axis of the OPEs. For example, each OPEmay be configured to redirect a portion of the light striking the OPE toan EPE of the same waveguide, while allowing the remaining portion ofthe light to continue to propagate down the waveguide. Upon impinging onthe OPE again, another portion of the remaining light is redirected tothe EPE, and the remaining portion of that portion continues topropagate further down the waveguide, and so on. Similarly, uponstriking the EPE, a portion of the impinging light is directed out ofthe waveguide towards the user, and a remaining portion of that lightcontinues to propagate through the waveguide until it strikes the EPagain, at which time another portion of the impinging light is directedout of the waveguide, and so on. Consequently, a single beam ofin-coupled light may be “replicated” each time a portion of that lightis redirected by an OPE or EPE, thereby forming a field of cloned beamsof light, as shown in FIG. 6. In some embodiments, the OPE and/or EPEmay be configured to modify a size of the beams of light.

Accordingly, with reference to FIGS. 9A and 9B, in some embodiments, theset 660 of waveguides includes waveguides 670, 680, 690; in-couplingoptical elements 700, 710, 720; light distributing elements (forexample, OPE's) 730, 740, 750; and out-coupling optical elements (forexample, EP's) 800, 810, 820 for each component color. The waveguides670, 680, 690 may be stacked with an air gap/cladding layer between eachone. The in-coupling optical elements 700, 710, 720 redirect or deflectincident light (with different in-coupling optical elements receivinglight of different wavelengths) into its waveguide. The light thenpropagates at an angle which will result in TIR within the respectivewaveguide 670, 680, 690. In the example shown, light ray 770 (forexample, blue light) is deflected by the first in-coupling opticalelement 700, and then continues to bounce down the waveguide,interacting with the light distributing element (for example, OPE's) 730and then the out-coupling optical element (for example, EPs) 800, in amanner described earlier. The light rays 780 and 790 (for example, greenand red light, respectively) will pass through the waveguide 670, withlight ray 780 impinging on and being deflected by in-coupling opticalelement 710. The light ray 780 then bounces down the waveguide 680 viaTIR, proceeding on to its light distributing element (for example, OPEs)740 and then the out-coupling optical element (for example, EP's) 810.Finally, light ray 790 (for example, red light) passes through thewaveguide 690 to impinge on the light in-coupling optical elements 720of the waveguide 690. The light in-coupling optical elements 720 deflectthe light ray 790 such that the light ray propagates to lightdistributing element (for example, OPEs) 750 by TIR, and then to theout-coupling optical element (for example, EPs) 820 by TIR. Theout-coupling optical element 820 then finally out-couples the light ray790 to the viewer, who also receives the out-coupled light from theother waveguides 670, 680.

FIG. 9C illustrates a top-down plan view of an example of the pluralityof stacked waveguides of FIGS. 9A and 9B. It will be appreciated thatthis top-down view may also be referred to as a head-on view, as seen inthe direction of propagation of light towards the in-coupling opticalelements 800, 810, 820; that is, the top-down view is a view of thewaveguides with image light incident normal to the page. As illustrated,the waveguides 670, 680, 690, along with each waveguide's associatedlight distributing element 730, 740, 750 and associated out-couplingoptical element 800, 810, 820, may be vertically aligned. However, asdiscussed herein, the in-coupling optical elements 700, 710, 720 are notvertically aligned; rather, the in-coupling optical elements arepreferably non-overlapping (for example, laterally spaced apart as seenin the top-down view). As discussed further herein, this nonoverlappingspatial arrangement facilitates the injection of light from differentsources into different waveguides on a one-to-one basis, therebyallowing a specific light source to be uniquely coupled to a specificwaveguide. In some embodiments, arrangements including nonoverlappingspatially-separated in-coupling optical elements may be referred to as ashifted pupil system, and the in-coupling optical elements within thesearrangements may correspond to sub-pupils.

It will be appreciated that the spatially overlapping areas may havelateral overlap of 70% or more, 80% or more, or 90% or more of theirareas, as seen in the top-down view. On the other hand, the laterallyshifted areas may have less than 30% overlap, less than 20% overlap, orless than 10% overlap of their areas, as seen in top-down view. In someembodiments, laterally shifted areas have no overlap.

FIG. 9D illustrates a top-down plan view of another example of aplurality of stacked waveguides. As illustrated, the waveguides 670,680, 690 may be vertically aligned. However, in comparison to theconfiguration of FIG. 9C, separate light distributing elements 730, 740,750 and associated out-coupling optical elements 800, 810, 820 areomitted. Instead, light distributing elements and out-coupling opticalelements are effectively superimposed and occupy the same area as seenin the top-down view. In some embodiments, light distributing elements(for example, OPE's) may be disposed on one major surface of thewaveguides 670, 680, 690 and out-coupling optical elements (for example,EPE's) may be disposed on the other major surface of those waveguides.Thus, each waveguide 670, 680, 690 may have superimposed lightdistributing and out coupling optical elements, collectively referred toas combined OPE/EPE's 1281, 1282, 1283, respectively. Further detailsregarding such combined OPE/EPE's may be found in U.S. application Ser.No. 16/221,359, filed on Dec. 14, 2018, the entire disclosure of whichis incorporated by reference herein. The in-coupling optical elements700, 710, 720 in-couple and direct light to the combined OPE/EPE's 1281,1282, 1283, respectively. In some embodiments, as illustrated, thein-coupling optical elements 700, 710, 720 may be laterally shifted (forexample, they are laterally spaced apart as seen in the illustratedtop-down view) and have a shifted pupil spatial arrangement. As with theconfiguration of FIG. 9C, this laterally-shifted spatial arrangementfacilitates the injection of light of different wavelengths (forexample, from different light sources) into different waveguides on aone-to-one basis.

FIG. 9E illustrates a top-down plan view of another example of aconfiguration for in-coupling optical elements 700, 710, 720. Asillustrated, the in-coupling optical elements 700, 710, 720 may beshifted such that they are spaced in a triangular formation when viewedfrom the top-down view. It will be appreciated that in thisconfiguration, the spatial arrangement of the in-coupling opticalelements 700, 710, 720 may match the spatial arrangement of one or morenanowire LED arrays 1030 a, 1030 b, 1030 c. In some embodiments, thesenanowire LED arrays 1030 a, 1030 b, 1030 c may be formed on a commonsubstrate or backplane 1093. In some embodiments, the nanowire LEDarrays 1030 a, 1030 b, 1030 c may each be configured to emit light of adifferent component color (for example, red, green, and blue).

FIG. 9F illustrates an example of wearable display system 60 into whichthe various waveguides and related systems disclosed herein may beintegrated. In some embodiments, the display system 60 is the system 250of FIG. 6, with FIG. 6 schematically showing some parts of that system60 in greater detail. For example, the waveguide assembly 260 of FIG. 6may be part of the display 70.

With continued reference to FIG. 9F, the display system 60 includes adisplay 70, and various mechanical and electronic modules and systems tosupport the functioning of that display 70. The display 70 may becoupled to a frame 80, which is wearable by a display system user orviewer 90 and which is configured to position the display 70 in front ofthe eyes of the user 90. The display 70 may be considered eyewear insome embodiments. In some embodiments, a speaker 100 is coupled to theframe 80 and configured to be positioned adjacent the ear canal of theuser 90 (in some embodiments, another speaker, not shown, may optionallybe positioned adjacent the other ear canal of the user to providestereo/shapeable sound control). The display system 60 may also includeone or more microphones 110 or other devices to detect sound. In someembodiments, the microphone is configured to allow the user to provideinputs or commands to the system 60 (for example, the selection of voicemenu commands, natural language questions, etc.), and/or may allow audiocommunication with other persons (for example, with other users ofsimilar display systems. The microphone may further be configured as aperipheral sensor to collect audio data (for example, sounds from theuser and/or environment). In some embodiments, the display system 60 mayfurther include one or more outwardly-directed environmental sensors 112configured to detect objects, stimuli, people, animals, locations, orother aspects of the world around the user. For example, environmentalsensors 112 may include one or more cameras, which may be located, forexample, facing outward so as to capture images similar to at least aportion of an ordinary field of view of the user 90. In someembodiments, the display system may also include a peripheral sensor 120a, which may be separate from the frame 80 and attached to the body ofthe user 90 (for example, on the head, torso, an extremity, etc. of theuser 90). The peripheral sensor 120 a may be configured to acquire datacharacterizing a physiological state of the user 90 in some embodiments.For example, the sensor 120 a may be an electrode.

With continued reference to FIG. 9F, the display 70 is operativelycoupled by communications link 130, such as by a wired lead or wirelessconnectivity, to a local data processing module 140 which may be mountedin a variety of configurations, such as fixedly attached to the frame80, fixedly attached to a helmet or hat worn by the user, embedded inheadphones, or otherwise removably attached to the user 90 (for example,in a backpack-style configuration, in a belt-coupling styleconfiguration). Similarly, the sensor 120 a may be operatively coupledby communications link 120 b, for example, a wired lead or wirelessconnectivity, to the local processor and data module 140. The localprocessing and data module 140 may include a hardware processor, as wellas digital memory, such as non-volatile memory (for example, flashmemory or hard disk drives), both of which may be utilized to assist inthe processing, caching, and storage of data. Optionally, the localprocessor and data module 140 may include one or more central processingunits (CPUs), graphics processing units (GPUs), dedicated processinghardware, and so on. The data may include data a) captured from sensors(which may be, for example, operatively coupled to the frame 80 orotherwise attached to the user 90), such as image capture devices (suchas cameras), microphones, inertial measurement units, accelerometers,compasses, GPS units, radio devices, gyros, and/or other sensorsdisclosed herein; and/or b) acquired and/or processed using remoteprocessing module 150 and/or remote data repository 160 (including datarelating to virtual content), possibly for passage to the display 70after such processing or retrieval. The local processing and data module140 may be operatively coupled by communication links 170, 180, such asvia a wired or wireless communication links, to the remote processingmodule 150 and remote data repository 160 such that these remote modules150, 160 are operatively coupled to each other and available asresources to the local processing and data module 140. In someembodiments, the local processing and data module 140 may include one ormore of the image capture devices, microphones, inertial measurementunits, accelerometers, compasses, GPS units, radio devices, and/orgyros. In some other embodiments, one or more of these sensors may beattached to the frame 80, or may be standalone structures thatcommunicate with the local processing and data module 140 by wired orwireless communication pathways.

With continued reference to FIG. 9F, in some embodiments, the remoteprocessing module 150 may include one or more processors configured toanalyze and process data and/or image information, for instanceincluding one or more central processing units (CPUs), graphicsprocessing units (GPUs), dedicated processing hardware, and so on. Insome embodiments, the remote data repository 160 may include a digitaldata storage facility, which may be available through the internet orother networking configuration in a “cloud” resource configuration. Insome embodiments, the remote data repository 160 may include one or moreremote servers, which provide information, for example, information forgenerating virtual content, to the local processing and data module 140and/or the remote processing module 150. In some embodiments, all datais stored and all computations are performed in the local processing anddata module, allowing fully autonomous use from a remote module.Optionally, an outside system (for example, a system of one or moreprocessors, one or more computers) that includes CPUs, GPUs, and so on,may perform at least a portion of processing (for example, generatingimage information, processing data) and provide information to, andreceive information from, modules 140, 150, 160, for instance viawireless or wired connections.

FIG. 10 illustrates an example of a wearable display system with a lightprojection system 910 having a spatial light modulator 930 and aseparate light source 940. The light source 940 may include one or morelight emitters and illuminates the spatial light modulator (SLM) 930. Alens structure 960 may be used to focus the light from the light source940 onto the SLM 930. A beam splitter (for example, a polarizing beamsplitter (PBS)) 950 reflects light from the light source 940 to thespatial light modulator 930, which reflects and modulates the light. Thereflected modulated light, also referred to as image light, thenpropagates through the beam splitter 950 to the eyepiece 920. Anotherlens structure, projection optics 970, may be utilized to converge orfocus the image light onto the eyepiece 920. The eyepiece 920 mayinclude one or more waveguides or waveguides that relay the modulated tothe eye 210.

As noted herein, the separate light source 940 and associated lensstructure 960 may undesirably add weight and size to the wearabledisplay system. This may decrease the comfort of the display system,particularly for a user wearing the display system for an extendedduration.

In addition, the light source 940 in conjunction with the SLM 930 mayconsume energy inefficiently. For example, the light source 940 mayilluminate the entirety of the SLM 930. The SLM 930 then selectivelyreflects light towards the eyepiece 920. thus, not all the lightproduced by the light source 940 may be utilized to form an image; someof this light, for example, light corresponding to dark regions of animage, is not reflected to the eyepiece 920. As a result, the lightsource 940 utilizes energy to generate light to illuminate the entiretyof the SLM 930, but only a fraction of this light may be needed to formsome images.

Moreover, as noted herein, in some cases, the SLM 930 may modulate lightusing a micro-mirror to selectively reflect incident light, or usingliquid crystal molecules that modify the amount of light reflected froman underlying mirror. As a result, such devices require physicalmovement of optical elements (for example, micro-mirrors or liquidcrystal molecules) in order to modulate light from the light source 940.The physical movement required to modulate light to encode the lightwith image information, for example, corresponding to a pixel, may occurat relatively slow speeds in comparison to, for example, the ability toturn an LED or OLED “on” or “off”. This relatively slow movement maylimit the frame rate of the display system and may be visible as, forexample, motion blur, color-breakup, and/or presented images that aremismatched with the pose of the user's head or changes in said pose.

Advantageously, wearable displays utilizing nanowire LED micro-displays,as disclosed herein, may facilitate wearable display systems that have arelatively low weight and bulkiness, high energy efficiency, and highframe rate, with low motion blur and low motion-to-photon latency. Lowblur and low motion-to-photon latency are further discussed in U.S.Provisional Application No. 62/786,199, filed Dec. 28, 2018, the entiredisclosure of which is incorporated by reference herein. In addition, incomparison to scanning fiber displays, the nanowire LED micro-displaysmay avoid artifacts caused by the use of coherent light sources.

With reference now to FIG. 11A, an example is illustrated of a wearabledisplay system with a light projection system 1010 having multiplenanowire LED micro-displays 1030 a, 1030 b, 1030 c. Light from themicro-displays 1030 a, 1030 b, 1030 c is combined by an optical combiner1050 and directed towards an eyepiece 1020, which relays the light tothe eye 210 of a user. Projection optics 1070 may be provided betweenthe optical combiner 1050 and the eyepiece 1020. In some embodiments,the eyepiece 1020 may be a waveguide assembly including one or morewaveguides. In some embodiments, the light projection system 1010 andthe eyepiece 1020 may be supported (for example, attached to) the frame80 (FIG. 9F).

In some embodiments, the micro-displays 1030 a, 1030 b, 1030 c may bemonochrome micro-displays, with each monochrome micro-display outputtinglight of a different component color to provide a monochrome image. Asdiscussed herein, the monochrome images combine to form a full-colorimage.

In some other embodiments, the micro-displays 1030 a, 1030 b, 1030 c mayeach be full-color displays configured to output light of all componentcolors. For example, the micro-displays 1030 a, 1030 b, 1030 c eachinclude red, green, and blue light emitters. The micro-displays 1030 a,1030 b, 1030 c may be identical and may display the same image. However,utilizing multiple micro-displays may provide advantages for increasingthe brightness and brightness dynamic range of the brightness of theimage, by combining the light from the multiple micro-displays to form asingle image. In some embodiments, two or more (for example, three)micro-displays may be utilized, with the optical combiner 1050 isconfigured to combine light from all of these micro-displays.

With continued reference to FIG. 11A, the micro-displays 1030 a, 1030 b,1030 c may each be configured to emit image light 1032 a, 1032 b, 1032c. Where the micro-displays are monochrome micro-displays, the imagelight 1032 a, 1032 b, 1032 c may each be of a different component color.The optical combiner 1050 receives the image light 1032 a, 1032 b, 1032c and effectively combines this light such that the light propagatesgenerally in the same direction, for example, toward the projectionoptics 1070. In some embodiments, the optical combiner 1050 may be adichroic X-cube prism having reflective internal surfaces that redirectthe image light 1032 a, 1032 b, 1032 c to the projection optics 1070. Itwill be appreciated that the projection optics 1070 may be a lensstructure including one or more lenses which converge or focus imagelight onto the eyepiece 1020. The eyepiece 1020 then relays the imagelight 1032 a, 1032 b, 1032 c to the eye 210.

In some embodiments, the eyepiece 1020 may include a plurality ofstacked waveguides 1020 a, 1020 b, 1020 c, each of which has arespective in-coupling optical element 1022 a, 1022 b, 1022 c. In someembodiments, the number of waveguides is proportional to the number ofcomponent colors provided by the micro-displays 1030 a, 1030 b, 1030 c.For example, where there are three component colors, the number ofwaveguides in the eyepiece 1020 may include a set of three waveguides ormultiple sets of three waveguides each. In some embodiments, each setmay output light with wavefront divergence corresponding to a particulardepth plane, as discussed herein. It will be appreciated that thewaveguides 1020 a, 1020 b, 1020 c and the in-coupling optical element1022 a, 1022 b, 1022 c may correspond to the waveguides 670, 680, 690and the in-coupling optical elements 700, 710, 720, respectively, ofFIGS. 9A-9C. As viewed from the projection optics 1070, the in-couplingoptical elements 1022 a, 1022 b, 1022 c may be laterally shifted, suchthat they at least partly do not overlap as seen in such a view.

As illustrated, the various in-coupling optical elements disclosedherein (for example, the in-coupling optical element 1022 a, 1022 b,1022 c) may be disposed on a major surface of an associated waveguide(for example, waveguides 1020 a, 1020 b, 1020 c, respectively). Inaddition, as also illustrated, the major surface on which a givenin-coupling optical element is disposed may be the rear surface of thewaveguide. In such a configuration, the in-coupling optical element maybe a reflective light redirecting element, which in-couples light byreflecting the light at angles which support TIR through the associatedwaveguide. In some other configurations, the in-coupling optical elementmay be disposed on the forward surface of the waveguide (closer to theprojection optics 1070 than the rearward surface). In suchconfigurations, the in-coupling optical element may be a transmissivelight redirecting element, which in-couples light by changing thedirection of propagation of light as the light is transmitted throughthe in-coupling optical element. It will be appreciated that any of thein-coupling optical elements disclosed herein may be reflective ortransmissive in-coupling optical elements.

With continued reference to FIG. 11A, image light 1032 a, 1032 b, 1032 cfrom different ones of the micro-displays 1030 a, 1030 b, 1030 c maytake different paths to the eyepiece 1020, such that they impinge ondifferent ones of the in-coupling optical element 1022 a, 1022 b, 1022c. Where the image light 1032 a, 1032 b, 1032 c includes light ofdifferent component colors, the associated in-coupling optical element1022 a, 1022 b, 1022 c, respectively, may be configured to selectivelyin couple light of different wavelengths, as discussed above regarding,for example, the in-coupling optical elements 700, 710, 720 of FIGS.9A-9C.

With continued reference to FIG. 11A, the optical combiner 1050 may beconfigured to redirect the image light 1032 a, 1032 b, 1032 c emitted bythe micro-displays 1030 a, 1030 b, 1030 c such that the image lightpropagates along different optical paths, in order to impinge on theappropriate associated one of the in-coupling optical element 1022 a,1022 b, 1022 c. Thus, the optical combiner 1050 combines the image light1032 a, 1032 b, 1032 c in the sense that the image light is outputtedfrom a common face of the optical combiner 1050, although light may exitthe optical combiner in slightly different directions. For example, thereflective internal surfaces 1052, 1054 of the X-cube prism may each beangled to direct the image light 1032 a, 1032 b, 1032 c along differentpaths to the eyepiece 1020. As a result, the image light 1032 a, 1032 b,1032 c may be incident on different associated ones of in-couplingoptical elements 1022 a, 1022 b, 1022 c. In some embodiments, themicro-displays 1030 a, 1030 b, 1030 c may be appropriately angledrelative to the reflective internal surfaces 1052, 1054 of the X-cubeprism to provide the desired light paths to the in-coupling opticalelements 1022 a, 1022 b, 1022 c. For example, faces of one or more ofthe micro-displays 1030 a, 1030 b, 1030 c may be angled to matchingfaces of the optical combiner 1050, such that image light emitted by themicro-displays is incident on the reflective internal surfaces 1052,1054 at an appropriate angle to propagate towards the associatedin-coupling optical element 1022 a, 1022 b, or 1022 c. In someembodiments, as discussed herein, micro-wire LEDs may advantageously beengineered to provide a directional light output. The dominant directionof light output for each of the micro-displays 1030 a, 1030 b, 1030 cmay be selected so that light propagates along the appropriate lightpath from each of these micro-displays to a corresponding one of thein-coupling optical elements 1022 a, 1022 b, and 1022 c. It will beappreciated that, in addition to a cube, the optical combiner 1050 maytake the form of various other polyhedra. For example, the opticalcombiner 1050 may be in the shape of a rectangular prism having at leasttwo faces that are not squares.

With continued reference to FIG. 11A, in some embodiments, themonochrome micro-display 1030 b directly opposite the output face 1051may advantageously output green light. It will be appreciated that thereflective surfaces 1052, 1054 may have optical losses when reflectinglight from the micro-displays. In addition, the human eye is mostsensitive to the color green. Consequently, the monochrome micro-display1030 b opposite the output face 1051 preferably outputs green light, sothat the green light may proceed directly through the optical combiner1050 without needing to be reflected to be outputted from the opticalcombiner 1050. It will be appreciated, however, that the greenmonochrome micro-display may face other surfaces of the optical combiner1050 in some other embodiments.

As discussed herein, the perception of a full color image by a user maybe achieved with time division multiplexing in some embodiments. Forexample, different ones of the nanowire LED micro-displays 1030 a, 1030b, 1030 c may be activated at different times to generate differentcomponent color images. In such embodiments, the different componentcolor images that form a single full color image may be sequentiallydisplayed sufficiently quickly that the human visual system does notperceive the component color images as being displayed at differenttimes; that is, the different component color images that form a singlefull color image may all be displayed within a duration that issufficiently short that the user perceives the component color images asbeing simultaneously presented, rather than being temporally separated.For example, it will be appreciated that the human visual system mayhave a flicker fusion threshold. The flicker fusion threshold may beunderstood to a duration within which the human visual system is unableto differentiate images as being presented at different times. Imagespresented within that duration are fused or combined and, as a result,may be perceived by a user to be present simultaneously. Flickeringimages with temporal gaps between the images that are outside of thatduration are not combined, and the flickering of the images isperceptible. In some embodiments, the duration is 1/60 seconds or less,which corresponds to a frame rate of 60 Hz or more. Preferably, imageframes for any individual eye are provided to the user at a frame rateequal to or higher than the duration of the flicker fusion threshold ofthe user. For example, the frame rate for each of the left-eye orright-eye pieces may be 60 Hz or more, or 120 Hz or more; and, as aresult, the frame rate provided by the light projection system 1010 maybe 120 Hz or more, or 240 Hz or more in some embodiments. It will beappreciated that time division multiplexing may advantageously reducethe computational load on processors (for example, graphics processors)utilized to form displayed images. In some other embodiments, such aswhere sufficient computational resources are available, all componentcolor images that form a full color image may be displayedsimultaneously by the micro-displays 1030 a, 1030 b, 1030 c.

As discussed herein, the micro-displays 1030 a, 1030 b, 1030 c may eachinclude arrays of nanowire LED light emitters for forming images. FIG.11B illustrates an example of an array 1042 of light emitters 1044.Where the associated micro-display is a monochrome micro-display, thelight emitters 1044 may all be configured to emit light of the samecolor.

Where the associated micro-display is a full-color micro-display,different ones of the light emitters 1044 may be configured to emitlight of different colors. In such embodiments, the light emitters 1044may be considered subpixels and may be arranged in groups, with eachgroup having at least one light emitter configured to emit light of eachcomponent color. For example, where the component colors are red, green,and blue, each group may have at least one red subpixel, at least onegreen subpixel, in at least one blue subpixel.

It will be appreciated, that while the light emitters 1044 are shownarranged in a grid pattern for ease of illustration, the light emitters1044 may have other regularly repeating spatial arrangements. Forexample, the number of light emitters of different component colors mayvary, the sizes of the light emitters may vary, the shapes of the lightemitters and/or the shapes made out by groups of light emitters mayvary, etc.

FIG. 11C illustrates a cross-sectional side view of the nanowire LEDarray 1042 of FIG. 11B. In some embodiments, the nanowire LED array 1042may include one or more nanowires 1094, which may be light-emittingdiode elements. In some embodiments, the nanowire array may be a uniformarray of nanowires 1094. As examples, the nanowires 1094 may haveheights of 10-10,000 nm, 100-1000 nm, 500-1000 nm, or 700-1000 nm, andwidth of, for example, 10-1000 nm, including 200 nm or less, or 100 nmor less and more than 10 nm.]] In some embodiments, the nanowires 1094may be cylindrical and the width may correspond to the diameter of thenanowires. The nanowires 1094 may be grouped into pixels defined byelectrical contacts 1095 shared by each group of nanowires 1094. It willbe appreciated that each group of nanowires 1094 forming a pixel mayshare a second electrical contact (not shown). Each pixel, which mayinclude a group of nanowires, may be an individual light emitter 1044.

With continued reference to FIG. 11C, nanowire LEDs may utilizeinorganic materials, for example, Group III-V materials such as GaAs,GaN, and/or GaIn, and may be on a substrate 1093, which may be abackplane containing various electronic devices, such as CMOS devicesfor the controlling operation of the nanowire LEDs. Examples of GaNmaterials include InGaN, which, in some embodiments, may be used to formblue or green light emitters. Although various embodiments may utilizeother materials, GaN may advantageously be used for generating theentire visible spectrum simply by controlling the In dopingconcentration, to obtain the desired electronic bandgap tuning, whichcauses the emission of desired wavelengths of light. Thus, the nanowiresmay be monochrome and each grouping may be made to emit the same color,or, by using different doping levels for different pixels, differentpixels may be made to emit light of different colors. As a result, blue,green and red emitters may all be formed on a single GaN semiconductor,thereby simplifying manufacturing and increasing manufacturingthroughput. Additionally, GaN and InGaN may be grown on standardsemiconductor materials such as silicon, which allows integration withrelated micro-electronics circuitry (CMOS Si backplanes) for driving thenanowire LED pixels.

Examples of GaIn materials include AlGaInP, which, in some embodiments,may be used to form red light emitters.

With reference now to FIG. 12, another example is illustrated of awearable display system with a light projection system having multiplenanowire LED micro-displays 1030 a, 1030 b, 1030 c. The illustrateddisplay system is similar to the display system of FIG. 11A except thatthe optical combiner 1050 has a standard X-cube prism configuration andincludes light redirecting structures 1080 a and 1080 c for modifyingthe angle of incidence of light on the reflective surfaces 1052, 1054 ofthe X-cube prism. It will be appreciated that a standard X-cube prismconfiguration will receive light which is normal to a face of the X-cubeand redirect this light 45° such that it is output at a normal anglefrom a transverse face of the X-cube. However, this would cause theimage light 1032 a, 1032 b, 1032 c to be incident on the samein-coupling optical element of the eyepiece 1020. In order to providedifferent paths for the image light 1032 a, 1032 b, 1032 c, so that theimage light is incident on associated ones of the in-coupling opticalelements 1022 a, 1022 b, 1022 c of the waveguide assembly, the lightredirecting structures 1080 a, 1080 c may be utilized.

In some embodiments, the light redirecting structures 1080 a, 1080 c maybe lens structures. It will be appreciated that the lens structures maybe configured to receive incident light and to redirect the incidentlight at an angle such that the light reflects off a corresponding oneof the reflective surfaces 1052, 1054 and propagates along a light pathtowards a corresponding one of the in-coupling optical elements 1022 a,1022 c. As examples, the light redirecting structures 1080 a, 1080 c mayinclude micro-lenses, nano-lenses, reflective wells, metasurfaces, andliquid crystal gratings. In some embodiments, the micro-lenses,nano-lenses, reflective wells, metasurfaces, and liquid crystal gratingsmay be organized in arrays. For example, each light emitter of themicro-displays 1030 a, 1030 c may be matched with one micro-lens. Insome embodiments, in order to redirect light in a particular direction,the micro-lens or reflective wells may be asymmetrical and/or the lightemitters may be disposed off-center relative to the micro-lens. Inaddition, in some embodiments, the light redirecting structures 1080 a,1080 c may be collimators which narrow the angular emission profiles ofassociated light emitters, to increase the amount of light ultimatelyin-coupled into the eyepiece 1020. Further details regarding such lightredirecting structures 1080 a, 1080 c are discussed below regardingFIGS. 24A-27C.

With continued reference to FIG. 12, in some embodiments, one or both ofthe light redirecting structures 1080 a, 1080 c may be omitted and thenanowire LEDs of the nanowire LED micro-displays 1030 a, 1030 b, 1030 cmay be configured to emit light with the desired directionality topropagate along a light path to the associated in-coupling opticalelements 1022 a, 1022 b, 1022 c. As discussed herein, the nanowire LEDsmay be engineered with a selected directionality, which may benon-normal to the light output surface of the associated micro-display.Thus, in some embodiments, the physical design and composition of thenanowire LEDs of each of the nanowire LED micro-displays 1030 a, 1030 b,1030 c may be selected to provide light output in a different direction,as illustrated.

With reference now to FIG. 13A, in some embodiments, two or more of thein-coupling optical elements 1022 a, 1022 b, 1022 c may overlap (forexample, as seen in a head-on view in the direction of light propagationinto the in-coupling optical element 1022 a, 1022 b, 1022 c). FIG. 13Aillustrates an example of a side-view of a wearable display system witha light projection system 1010 having multiple nanowire LEDmicro-displays 1032 a, 1032 b, 1032 c and an eyepiece 1020 withoverlapping light in-coupling optical elements 1022 a, 1022 c andnon-overlapping light in-coupling optical element 1022 b. Asillustrated, the in-coupling optical elements 1022 a, 1022 c overlap,while the in-coupling optical elements 1022 b are laterally shifted.Stated another way, the in-coupling optical elements 1022 a, 1022 c arealigned directly in the paths of the image light 1032 a, 1032 c, whilethe image light 1032 b follows another path to the eyepiece 1020, suchthat it is incident on an area of the eyepiece 1020 that is laterallyshifted relative to the area in which the image light 1032 a, 1032 c isincident.

As illustrated, differences between the paths for the image light 1032 band image light 1032 a, 1032 c may be established using lightredirecting structures 1080 a, 1080 c. In some embodiments, the imagelight 1032 b from the nanowire LED micro-display 1030 b proceedsdirectly through the optical combiner 1052. The image light 1032 a fromthe nanowire LED micro-display 1032 a is redirected by the lightredirecting structure 1080 a such that it reflects off of the reflectivesurface 1054 and propagates out of the optical combiner 1050 in the samedirection as the image light 1032 c. It will be appreciated that theimage light 1032 c from the nanowire LED micro-display 1032 c isredirected by the light redirecting structure 1080 c such that itreflects off of the reflective surface 1052 at an angle such that theimage light 1032 c propagates out of the optical combiner 1050 in thesame direction as the image light 1032 b. Thus, the redirection of lightby the light redirecting structures 1080 a, 1080 c and the angles of thereflective surfaces 1052, 1054 are configured to provide a common pathfor the image light 1032 a, 1032 c out of the optical combiner 1050,with this common path being different from the path of the image light1032 b. In some other embodiments, one or both of the light redirectingstructures 1080 a, 1080 c may be omitted and the reflective surfaces1052, 1054 in the optical combiner 1050 may be configured to reflect theimage light 1032 a, 1032 c in the appropriate respective directions suchthat they exit the optical combiner 1050 propagating in the samedirection, which is different from the direction of the image light 1032b. As such, after propagating through the projection optics 1070, theimage light 1032 a, 1032 c exit from one exit pupil while the imagelight 1032 b exits from another exit pupil. In this configuration, thelight projection system 1010 may be referred to as a two-pupilprojection system.

In some embodiments, the light projection system 1010 may have a singleoutput pupil and may be referred to as a single-pupil projection system.In such embodiments, the light projection system 1010 may be configuredto direct the image light 1032 a, 1032 b, 1032 c onto a single commonarea of the eyepiece 1020. Such a configuration is shown in FIG. 13B,which illustrates a wearable display system with a light projectionsystem 1010 having multiple nanowire LED micro-displays 1030 a, 1030 b,1030 c configured to direct light to a single light in-coupling area ofthe eyepiece 1020. In some embodiments, as discussed further herein, theeyepiece 1020 may include a stack of waveguides having overlapping lightin-coupling optical elements. In some other embodiments, a single lightin-coupling optical element may be configured to in-couple light of allcomponent colors into a single waveguide. In some embodiments, thesingle waveguide may be formed of an optically transmissive highrefractive index material, for example silicon carbide (SiC).

The display system of FIG. 13B is similar to the display system of FIG.13A, except for the omission of the light redirecting structures 1080 a,1080 c and the use of the in-coupling optical element 1122 a and withthe associated waveguide 1020 a. As illustrated, the in-coupling opticalelement 1122 a in-couples each of image light 1032 a, 1032 b, 1032 cinto the waveguide 1020 a, which then relays the image light to the eye210. In some embodiments, the in-coupling optical element 1122 a mayinclude a diffractive grating. In some embodiments, the in-couplingoptical element 1122 a is a metasurface and/or liquid crystal grating.

In some other embodiments, the waveguide 1020 a may include two or morespaced-apart in-coupling optical elements, and each of the two or morespaced-apart in-coping optical elements may be configured to in-couplelight of different ranges of wavelengths (for example different colors).It will be appreciated that spaced-apart in-coupling optical elementsmay be spatially separated, as seen in a top-down plan view (as viewedhead-on in the direction of light impinging on the waveguide 1020 a).For example, the waveguide 1020 a may include the in-coupling opticalelements 1022 a, 1022 b, 1022 c on that single waveguide (for example,arranged as shown in FIG. 11A (in a side view), or FIG. 9C or 9D (in atop-down view), although spatially-separated on the same waveguide 1020a), with the in-coupling optical elements spatially separated so thatimage light of different colors from the light projection system 1010impinge uniquely on the associated one of the in-coupling opticalelements 1022 a, 1022 b, 1022 c. In some embodiments, twospatially-separated in-coupling optical elements may be utilized, withat least one of the in-coupling optical elements configured to in-couplelight of multiple different colors. For example, in such an arrangement,the in-coupling optical elements may be arranged in a similar manner tothe in-coupling elements 1022 a, 1022 b of FIG. 13A (in a side view),although spatially-separated on the same waveguide 1020 a.

As discussed herein, in some embodiments, the nanowire LEDmicro-displays 1030 a, 1030 b, 1030 c may be monochrome micro-displaysconfigured to emit light of different colors. In some embodiments, oneor more of the nanowire LED micro-displays 1030 a, 1030 b, 1030 c mayhave groups of light emitters configured to emit light of two or more,but not all, component colors. For example, a single nanowire LEDmicro-display may have groups of light emitters—with at least one lightemitter per group configured to emit blue light and at least one lightemitter per group configured to emit green light—and a separate nanowireLED micro-display on a different face of the X-cube 1050 may have lightemitters configured to emit red light. In some other embodiments, thenanowire LED micro-displays 1030 a, 1030 b, 1030 c may each befull-color displays, each having light emitters of all component colors.As noted herein, utilizing multiple similar micro-displays may provideadvantages for dynamic range and increased display brightness.

In some embodiments, a single full-color nanowire LED micro-display maybe utilized. FIG. 14 illustrate examples of a wearable display systemwith a single nanowire LED micro-display 1030 b. The wearable displaysystem of FIG. 14 is similar to the wearable display system of FIGS. 13Aand 13B, except that the single nanowire LED micro-display 1030 b is afull color micro-display configured to emit light of all componentcolors. As illustrated, the micro-display 1030 b emits image light 1032a, 1032 b, 1032 c of each component color. In such embodiments, theoptical combiner 1050 (FIG. 13B) may be omitted, which mayadvantageously reduce the weight and size of the wearable display systemrelative to a system with an optical combiner.

As discussed above, the in-coupling optical elements of the eyepiece1020 may assume various configurations. Some examples of configurationsfor the eyepiece 1020 are discussed below in relation to FIGS. 15-23C.

FIG. 15 illustrates a side view of an example of an eyepiece 1020 havinga stack of waveguides 1020 a, 1020 b, 1020 c with overlappingin-coupling optical elements 1022 a, 1022 b, 1022 c, respectively. Itwill be appreciated that the illustrated waveguide stack may be utilizedin place of the single illustrated waveguide 1020 a of FIGS. 13B and 14.As discussed herein, each of the in-coupling optical elements 1022 a,1022 b, 1022 c is configured to in-couple light having a specific color(for example, light of a particular wavelength, or a range ofwavelengths). In the illustrated orientation of the eyepiece 1020 inwhich the image light propagates vertically down the page towards theeyepiece 1020, the in-coupling optical elements 1022 a, 1022 b, 1022 care vertically aligned with each other (for example, along an axisparallel to the direction of propagation of the image light 1032 a, 1032b, 1032 c) such that they spatially overlap with each other as seen in atop down view (a head-on view in a direction of the image light 1032 a,1032 b, 1032 c propagating to the in-coupling optical elements).

With continued reference to FIG. 15, as discussed herein, the projectionsystem 1010 (FIGS. 13, 14) is configured to output a first monochromecolor image, a second monochrome color image, and a third monochromecolor image (for example, red, green and blue color images) through thesingle-pupil of the projection system, the monochrome images beingformed by the image light 1032 a, 1032 b, 1032 c, respectively. Thein-coupling optical element 1022 c is configured to in-couple the imagelight 1032 c for the first color image into the waveguide 1020 c suchthat it propagates through the waveguide 1020 c by multiple totalinternal reflections at the upper and bottom major surfaces of thewaveguide 1020 c, the in-coupling optical element 1022 b is configuredto in-couple the image light 1032 b for the second color image into thewaveguide 1020 b such that it propagates through the waveguide 1020 b bymultiple total internal reflections at the upper and bottom majorsurfaces of the waveguide 1020 b, and the in-coupling optical element1022 a is configured to in-couple the image light 1032 a for the thirdcolor image into the waveguide 1020 a such that it propagates throughthe waveguide 1020 a by multiple total internal reflections at the upperand bottom major surfaces of the waveguide 1020 a.

As discussed herein, the in-coupling optical element 1022 c ispreferably configured to in-couple substantially all the incident light1032 c corresponding to the first color image into the associatedwaveguide 1020 c while allowing substantially all the incident light1032 b, 1032 a corresponding to the second color image and the thirdcolor image, respectively, to be transmitted without being in-coupled.Similarly, the in-coupling optical element 1022 b is preferablyconfigured to in-couple substantially all the incident image light 1032b corresponding to the second color image into the associated waveguide1020 b while allowing substantially all the incident light correspondingto the third color image to be transmitted without being in-coupled.

It will be appreciated that, in practice, the various in-couplingoptical elements may not have perfect selectivity. For example, some ofthe image light 1032 b, 1032 a may undesirably be in-coupled into thewaveguide 1020 c by the in-coupling optical element 1022 c; and some ofthe incident image light 1032 a may undesirably be in-coupled into thewaveguide 1020 b by the in-coupling optical element 1022 b. Furthermore,some of the image light 1032 c may be transmitted through thein-coupling optical element 1022 c and in-coupled into waveguides 1020 band/or 1020 a by the in-coupling optical elements 1020 b and/or 1020 a,respectively. Similarly, some of the image light 1032 b may betransmitted through the in-coupling optical element 1022 b andin-coupled into waveguide 1020 a by the in-coupling optical element 1022a.

In-coupling image light for a color image into an unintended waveguidemay cause undesirable optical effects, such as, for example cross-talkand/or ghosting. For example, in-coupling of the image light 1032 c forthe first color image into unintended waveguides 1020 b and/or 1020 amay result in undesirable cross-talk between the first color image, thesecond color image and/or the third color image; and/or may result inundesirable ghosting. As another example, in-coupling of the image light1032 b, 1032 a for the second or third color image, respectively, intothe unintended waveguide 1020 c may result in undesirable cross-talkbetween the first color image, the second color image and/or the thirdcolor image; and/or may cause undesirable ghosting. In some embodiments,these undesirable optical effects may be mitigated by providing colorfilters (for example, absorptive color filters) that may reduce theamount of incident light that is in-coupled into an unintendedwaveguide.

FIG. 16 illustrates a side view of an example of a stack of waveguideswith color filters for mitigating ghosting or crosstalk betweenwaveguides. The eyepiece 1020 of FIG. 16 is similar to that of FIG. 15,except for the presence of one or more of the color filters 1024 c, 1024b and 1028, 1026. The color filters 1024 c, 1024 b are configured toreduce the amount of light unintentionally in-coupled into thewaveguides 1020 b and 1020 a, respectively. The color filters 1028, 1026are configured to reduce the amount of unintentionally in-coupled imagelight which propagates through the waveguides 1020 b, 1020 c,respectively.

With continued reference to FIG. 16, a pair of color filters 1026disposed on the upper and lower major surfaces of the waveguide 1020 cmay be configured to absorb image light 1032 a, 1032 b that may havebeen unintentionally been in-coupled into waveguide 1020 c. In someembodiments, the color filter 1024 c disposed between the waveguides1020 c and 1020 b is configured to absorb image light 1032 c that istransmitted through the in-coupling optical element 1022 c without beingin-coupled. A pair of color filters 1028 disposed on the upper and lowermajor surfaces of the waveguide 1020 b is configured to absorb imagelight 1032 a that is in-coupled into waveguide 1020 b. A color filter1024 b disposed between the waveguides 1020 b and 1020 a is configuredto absorb image light 1032 b that is transmitted through the in-couplingoptical element 710.

In some embodiments, the color filters 1026 on each major surface of thewaveguide 1020 c are similar and are configured to absorb light of thewavelengths of both image light 1032 a, 1032 b. In some otherembodiments, the color filter 1026 on one major surface of the waveguide1020 c may be configured to absorb light of the color of image light1032 a, and the color filter on the other major surface may beconfigured to absorb light of the color of image light 1032 b. In eitherarrangement, the color filters 1026 may be configured to selectivelyabsorb the image light 1032 a, 1032 b propagating through the waveguide1020 c by total internal reflection. For example, at TIR bounces of theimage light 1032 a, 1032 b off the major surfaces of the waveguide 1020c, the image light 1032 a, 1032 b contacts a color filter 1026 on thosemajor surfaces and a portion of that image light is absorbed.Preferably, due to the selective absorption of image light 1032 a, 1032b by the color filters 1026, the propagation of the in-coupled the imagelight 1032 c via TIR through the waveguide 1020 c is not appreciablyaffected.

Similarly, the plurality of color filters 1028 may be configured asabsorption filters that absorb in-coupled image light 1032 a thatpropagates through the waveguide 1020 b by total internal reflection. AtTIR bounces of the image light 1032 a off the major surfaces of thewaveguide 1020 b, the image light 1032 a contacts a color filter 1028 onthose major surfaces and a portion of that image light is absorbed.Preferably, the absorption of the image light 1032 a is selective anddoes not affect the propagation of the in-coupled image light 1032 bthat is also propagating via TIR through the waveguide 1020 b.

With continued reference to FIG. 16, the color filters 1024 c and 1024 bmay also be configured as absorption filters. The color filter 1024 cmay be substantially transparent to light of the colors of the imagelight 1032 a, 1032 b such that the image light 1032 a, 1032 b istransmitted through the color filter 1024 c with little to noattenuation, while light of the color of the image light 1032 c isselectively absorbed. Similarly, the color filter 1024 b may besubstantially transparent to light of the color of the image light 1032a such that incident image light 1032 a is transmitted through the colorfilter 1024 b with little to no attenuation, while light of the color ofthe image light 1032 b is selectively absorbed. The color filter 1024 cmay be disposed on a major surface (for example, the upper majorsurface) of the waveguide 1020 b as shown in FIG. 16. Alternately, thecolor filter 1024 c may be disposed on a separate substrate positionedbetween the waveguides 1020 c and 1020 b. Likewise, the color filter1024 b may be disposed on a major surface (for example, an upper majorsurface) of the waveguide 1020 a. Alternately, the color filter 1024 bmay be disposed on a separate substrate positioned between thewaveguides 1020 b and 1020 a. It will be appreciated that the colorfilters 1024 c and 1024 b may be vertically aligned with thesingle-pupil of the projector that outputs the image light 1032 a, 1032b, 1032 c (in orientations where the image light 1032 a, 1032 b, 1032 cpropagates vertically to the waveguide stack 1020, as illustrated).

In some embodiments, the color filters 1026 and 1028 may havesingle-pass attenuation factors of less than about 10%, (for example,less than or equal to about 5%, less than or equal to about 2%, andgreater than about 1%) to avoid significant undesired absorption oflight propagating through the thickness the waveguides 1020 c, 1020 b(for example, light of the colors of the image light 1032 a, 1032 bpropagating through the waveguides 1020 c, 1020 b from the ambientenvironment and/or other waveguides). Various embodiments of the colorfilters 1024 c and 1024 b may be configured to have low attenuationfactors for the wavelengths that are to be transmitted and highattenuation factor for the wavelengths that are to be absorbed. Forexample, in some embodiments, the color filter 1024 c may be configuredto transmit greater than 80%, greater than 90%, or greater than 95%, ofincident light having the colors of the image light 1032 a, 1032 b andabsorb greater than 80%, greater than 90%, or greater than 95%, ofincident light having the color of the image light 1032 a. Similarly,the color filter 1024 b may be configured to transmit greater than 80%,greater than 90%, or greater than 95%, of incident light having thecolor of the image light 1032 a and absorb greater than 80%, greaterthan 90%, or greater than 95%, of incident light having the color of theimage light 1032 b.

In some embodiments, the color filters 1026, 1028, 1024 c, 1024 b mayinclude a layer of color selective absorbing material deposited on oneor both surfaces of the waveguide 1020 c, 1020 b and/or 1020 a. Thecolor selective absorbing material may include a dye, an ink, or otherlight absorbing material such as metals, semiconductors, anddielectrics. In some embodiments, the absorption of material such asmetals, semiconductors, and dielectrics may be made color selective byutilizing these materials to form subwavelength gratings (for example, agrating that does not diffract the light). The gratings may be made ofplasmonics (for example gold, silver, and aluminum) or semiconductors(for example silicon, amorphous silicon, and germanium).

The color selective material may be deposited on the substrate usingvarious deposition methods. For example, the color selective absorbingmaterial may be deposited on the substrate using jet depositiontechnology (for example, ink-jet deposition). Ink-jet deposition mayfacilitate depositing thin layers of the color selective absorbingmaterial. Because ink-jet deposition allows for the deposition to belocalized on selected areas of the substrate, ink-jet depositionprovides a high degree of control over the thicknesses and compositionsof the layers of the color selective absorbing material, includingproviding for nonuniform thicknesses and/or compositions across thesubstrate. In some embodiments, the color selective absorbing materialdeposited using ink-jet deposition may have a thickness between about 10nm and about 1 micron (for example, between about 10 nm and about 50 nm,between about 25 nm and about 75 nm, between about 40 nm and about 100nm, between about 80 nm and about 300 nm, between about 200 nm and about500 nm, between about 400 nm and about 800 nm, between about 500 nm andabout 1 micron, or any value in a range/sub-range defined by any ofthese values). Controlling the thickness of the deposited layer of thecolor selective absorbing material may be advantageous in achieving acolor filter having a desired attenuation factor. Furthermore, layershaving different thickness may be deposited in different portions of thesubstrate. Additionally, different compositions of the color selectiveabsorbing material may be deposited in different portions of thesubstrate using ink-jet deposition. Such variations in compositionand/or thickness may advantageously allowing for location-specificvariations in absorption. For example, in areas of a waveguide in whichtransmission of light from the ambient (to allow the viewer to see theambient environment) is not necessary, the composition and/or thicknessmay be selected to provide high absorption or attenuation of selectedwavelengths of light. Other deposition methods such as coating,spin-coating, spraying, etc. may be employed to deposit the colorselective absorbing material on the substrate.

FIG. 17 illustrates an example of a top-down view of the waveguideassemblies of FIGS. 15 and 16. As illustrated, in-coupling opticalelements 1022 a, 1022 b, 1022 c spatially overlap. In addition, thewaveguides 1020 a, 1020 b, 1020 c, along with each waveguide'sassociated light distributing element 730, 740, 750 and associatedout-coupling optical element 800, 810, 820, may be vertically aligned.The in-coupling optical elements 1022 a, 1022 b, 1022 c are configuredto in-couple incident image light 1032 a, 1032 b, 1032 c (FIGS. 15 and16), respectively, in waveguides 1020 a, 1020 b, 1020 c, respectively,such that the image light propagates towards the associated lightdistributing element 730, 740, 750 by TIR.

FIG. 18 illustrates another example of a top-down view of the waveguideassemblies of FIGS. 15 and 16. As in FIG. 17, in-coupling opticalelements 1022 a, 1022 b, 1022 c spatially overlap and the waveguides1020 a, 1020 b, 1020 c are vertically aligned. In place of eachwaveguide's associated light distributing element 730, 740, 750 andassociated out-coupling optical element 800, 810, 820, however, arecombined OPE/EPE's 1281, 1282, 1283, respectively. The in-couplingoptical elements 1022 a, 1022 b, 1022 c are configured to in-coupleincident image light 1032 a, 1032 b, 1032 c (FIGS. 15 and 16),respectively, in waveguides 1020 a, 1020 b, 1020 c, respectively, suchthat the image light propagates towards the associated combinedOPE/EPE's 1281, 1282, 1283 by TIR.

While FIGS. 15-18 show overlapping in-coupling optical elements for asingle-pupil configuration of the display system, it will be appreciatedthat the display system may have a two-pupil configuration in someembodiments. In such a configuration, where three component colors areutilized, image light for two colors may have overlapping in-couplingoptical elements, while image light for a third color may have alaterally-shifted in-coupling optical element. For example, the opticalcombiner 1050 (FIGS. 11A, 12, 13A-13B) and/or light redirectingstructures 1080 a, 1080 c may be configured to direct image lightthrough the projection optics 1070 such that image light of two colorsare incident on directly overlapping areas of the eyepiece 1020 whileanother color of the image light is incident on an area that islaterally-shifted. For example, the reflective surfaces 1052, 1054 (FIG.11A) may be angled such that image light of one color follows a commonlight path with image light from the nanowire LED micro-display 1030 b,while image light of another color follows a different light path. Insome embodiments, rather than having both light redirecting structures1080 a, 1080 c (FIG. 12), one of these light redirecting structures maybe omitted, so that only light from one of the micro-displays 1030 a,1030 c is angled to provide a different light path from the lightemitted by the other two micro-displays.

FIG. 19A illustrates a side view of an example of an eyepiece having astack of waveguides with some overlapping and some laterally-shiftedin-coupling optical elements. The eyepiece of FIG. 19A is similar to theeyepiece of FIG. 15, except that one of the in-coupling optical elementsis laterally shifted relative to the other in-coping optical elements.In the illustrated orientation of the eyepiece 1020 in which the imagelight propagates vertically down the page towards the eyepiece 1020, thein-coupling optical elements 1022 a, 1022 c are vertically aligned witheach other (for example, along an axis parallel to the direction ofpropagation of the image light 1032 a, 1032 c) such that they spatiallyoverlap with each other as seen in a head-on view in a direction of theimage light 1032 a, 1032 c propagating to the in-coupling opticalelements 1022 a, 1022 b, 1022 c. As seen in the same head-on view (forexample, as seen in a top-down view in the illustrated orientation), thein-coupling optical element 1022 b is shifted laterally relative to theother in-coupling optical elements 1022 a, 1022 c. Light for thein-coupling optical element 1022 b is output to the eyepiece 1020through a different exit pupil than light for the in-coupling opticalelements 1022 a, 1022 c. It will be appreciated that the illustratedwaveguide stack including the waveguides 1020 a, 1020 b, 1020 c may beutilized in place of the single illustrated waveguide 1020 a of FIGS.13A, 13B, and 14.

With continued reference to FIG. 19A, the in-coupling optical element1022 c is configured to in-couple the image light 1032 c into thewaveguide 1020 c such that it propagates through the waveguide 1020 c bymultiple total internal reflections between the upper and bottom majorsurfaces of the waveguide 1020 c, the in-coupling optical element 1022 bis configured to in-couple the image light 1032 b into the waveguide1020 b such that it propagates through the waveguide 1020 b by multipletotal internal reflections between the upper and bottom major surfacesof the waveguide 1020 b, and the in-coupling optical element 1022 a isconfigured to in-couple the image light 1032 a into the waveguide 1020 asuch that it propagates through the waveguide 1020 a by multiple totalinternal reflections between the upper and bottom major surfaces of thewaveguide 1020 a.

The in-coupling optical element 1022 c is preferably configured toin-couple all the incident light 1032 c into the associated waveguide1020 c while being transmissive to all the incident light 1032 a. On theother hand, the image light 1032 b may propagate to the in-couplingoptical element 1022 b without needing to propagate through any otherin-coupling optical elements. This may be advantageous in someembodiments by allowing light, to which the eye is more sensitive, to beincident on a desired in-coupling optical element without any loss ordistortion associated with propagation through other in-coupling opticalelements. Without being limited by theory, in some embodiments, theimage light 1032 b is green light, to which the human eye is moresensitive. It will be appreciated that, while the waveguides 1020 a,1020 b, 1020 c are illustrated arranged a particular order, in someembodiments, the order of the waveguides 1020 a, 1020 b, 1020 c maydiffer.

It will be appreciated that, as discussed herein, the in-couplingoptical element 1022 c overlying the in-coupling optical elements 1022 amay not have perfect selectivity. Some of the image light 1032 a mayundesirably be in-coupled into the waveguide 1020 c by the in-couplingoptical element 1022 c; and some of the image light 1032 c may betransmitted through the in-coupling optical element 1022 c, after whichthe image light 1032 c may strike the in-coupling optical element 1020 aand be in-coupled into the waveguide 1020 a. As discussed herein, suchundesired in-coupling may be visible as ghosting or crosstalk.

FIG. 19B illustrates a side view of an example of the eyepiece of FIG.19A with color filters for mitigating ghosting or crosstalk betweenwaveguides. In particular, color filters 1024 c and/or 1026 are added tothe structures shown in FIG. 19A. As illustrated, the in-couplingoptical element 1022 c may unintentionally in-couple a portion of theimage light 1032 a into the waveguide 1020 c. In addition, oralternatively, a portion of the image light 1032 c undesirably betransmitted through the in-coupling optical element 1022 c after whichit may unintentionally be in-coupled by the in-coupling optical element1022 a.

To mitigate unintentionally in-couple image light 1032 a propagatingthrough the waveguide 1022 c, absorptive color filters 1026 may beprovided on one or both major surfaces of the waveguide 1022 c. Theabsorptive color filters 1026 may be configured to absorb light of thecolor of the unintentionally in-coupled image light 1032 a. Asillustrated, the absorptive color filters 1026 are disposed in thegeneral direction of propagation of the image light through thewaveguide 1020 c. Thus, the absorptive color filters 1026 are configuredto absorb image light 1032 a as that light propagates through thewaveguide 1020 c by TIR and contacts the absorptive color filters 1026while reflecting off one or both of the major surfaces of the waveguide1020 c.

With continued reference to FIG. 19B, to mitigate image light 1032 cwhich propagates through the in-coupling optical element 1022 c withoutbeing in-coupled, the absorptive color filter 1024 c may be providedforward of the in-coupling optical element 1022 a. The absorptive colorfilter 1024 c is configured to absorb light of the color of the imagelight 1032 c, to prevent that light from propagating to the in-couplingoptical element 1022 a. While illustrated between the waveguides 1020 cand 1020 b, in some other embodiments, the absorptive color filter 1024c may be disposed between the waveguides 1020 b and 1020 a. It will beappreciated that further details regarding the composition, formation,and properties of the absorptive color filters 1024 c and 1026 areprovided in the discussion of FIG. 16.

It will also be appreciated that in the embodiments illustrated in FIGS.16 and 19B, one or more of the color filters 1026, 1028, 1024 c, and1024 b may be omitted if one or more in-coupling optical elements 1022a, 1022 b, 1022 c have sufficiently high selectivity for the color ofthe light that is intended to be in-coupled into the associatedwaveguide 1020 a, 1020 b, 1022 c, respectively.

FIG. 20A illustrates an example of a top-down view of the eyepieces ofFIGS. 19A and 19B. As illustrated, in-coupling optical elements 1022 a,1022 c spatially overlap, while in-coupling optical element 1022 b islaterally-shifted. In addition, the waveguides 1020 a, 1020 b, 1020 c,along with each waveguide's associated light distributing element 730,740, 750 and associated out-coupling optical element 800, 810, 820, maybe vertically aligned. The in-coupling optical elements 1022 a, 1022 b,1022 c are configured to in-couple incident image light 1032 a, 1032 b,1032 c (FIGS. 15 and 16), respectively, in waveguides 1020 a, 1020 b,1020 c, respectively, such that the image light propagates towards theassociated light distributing element 730, 740, 750 by TIR.

FIG. 20B illustrates another example of a top-down view of the waveguideassembly of FIGS. 19A and 19B. As in FIG. 20A, in-coupling opticalelements 1022 a, 1022 c spatially overlap, the in-coupling opticalelement is laterally-shifted, and the waveguides 1020 a, 1020 b, 1020 care vertically aligned. In place of each waveguide's associated lightdistributing element 730, 740, 750 and associated out-coupling opticalelement 800, 810, 820, however, are combined OPE/EPE's 1281, 1282, 1283,respectively. The in-coupling optical elements 1022 a, 1022 b, 1022 care configured to in-couple incident image light 1032 a, 1032 b, 1032 c(FIGS. 15 and 16), respectively, in waveguides 1020 a, 1020 b, 1020 c,respectively, such that the image light propagates towards theassociated combined OPE/EPE's 1281, 1282, 1283 by TIR.

With reference now to FIG. 21, it will be appreciated that re-bounce ofin-coupled light may undesirably occur in waveguides. Re-bounce occurswhen in-coupled light propagating along a waveguide strikes thein-coupling optical element a second or subsequent time after theinitial in-coupling incidence. Re-bounce may result in a portion of thein-coupled light being undesirably out-coupled and/or absorbed by amaterial of the in-coupling optical element. The out-coupling and/orlight absorption undesirably may cause a reduction in overallin-coupling efficiency and/or uniformity of the in-coupled light.

FIG. 21 illustrates a side view of an example of re-bounce in awaveguide 1030 a. As illustrated, image light 1032 a is in-coupled intothe waveguide 1030 a by in-coupling optical element 1022 a. In-couplingoptical element 1022 a redirects the image light 1032 a such that itgenerally propagates through the waveguide in the direction 1033.Re-bounce may occur when in-coupled image light internally reflects orbounces off a major surface of the waveguide 1030 a opposite thein-coupling optical element 1022 a and is incident on or experiences asecond bounce (a re-bounce) at the in-coupling optical element 1022 a.The distance between two neighboring bounces on the same surface of thewaveguide 1030 a is indicated by spacing 1034.

Without being limited by theory, it will be appreciated that thein-coupling optical element 1022 a may behave symmetrically; that is, itmay redirect incident light such that the incident light propagatesthrough the waveguide at TIR angles. However, light that is incident onthe diffractive optical elements at TIR angles (such as upon re-bounce)may also be out-coupled. In addition or alternatively, in embodimentswhere the in-coupling optical element 1022 a is coated with a reflectivematerial, it will be understood that the reflection of light off of alayer of material such as metal may also involve partial absorption ofthe incident light, since reflection may involve the absorption andemission of light from a material. As a result, light out-couplingand/or absorption may undesirably cause loss of in-coupled light.Accordingly, re-bounced light may incur significant losses, as comparedwith light that interacts only once with the in-coupling optical element1022 a.

In some embodiments, the in-coupling elements are configured to mitigatein-coupled image light loss due to re-bounce. Generally, re-bounce ofin-coupled light occurs towards the end 1023 of the in-coupling opticalelement 1022 a in the propagation direction 1033 of the in-coupledlight. For example, light in-coupled at the end of the in-couplingoptical element 1022 a opposite the end 1023 may re-bounce if thespacing 1034 for that light is sufficiently short. To avoid suchre-bounce, in some embodiments, the in-coupling optical element 1022 ais truncated at the propagation direction end 1023, to reduce the width1022 w of the in-coupling optical element 1022 a along which re-bounceis likely to occur. In some embodiments, the truncation may be acomplete truncation of all structures of the in-coupling optical element1022 a (for example, the metallization and diffractive gratings). Insome other embodiments, for example, where the in-coupling opticalelement 1022 a includes a metalized diffraction grating, a portion ofthe in-coupling optical element 1022 a at the propagation direction end1023 may not be metalized, such that the propagation direction end 1023of the in-coupling optical element 1022 a absorbs less re-bouncing lightand/or outcouples re-bouncing light with a lower efficiency. In someembodiments, a diffractive region of an in-coupling optical element 1022a may have a width along a propagation direction 1033 shorter than itslength perpendicular to the propagation direction 1033, and/or may besized and shaped such that a first portion of image light 1032 a isincident on the in-coupling optical element 1022 a and a second portionof the beam of light impinges on the waveguide 1030 a without beingincident on the in-coupling optical element 1022 a. While waveguide 1032a and light in-coupling optical element 1022 a are illustrated alone forclarity, it will be appreciated that re-bounce and the strategiesdiscussed for reducing re-bounce may apply to any of the in-couplingoptical elements disclosed herein. It will also be appreciated that thespacing 1034 is related to the thickness of the waveguide 1030 a (alarger thickness results in a larger spacing 1034). In some embodiments,the thickness of individual waveguides may be selected to set thespacing 1034 such that re-bounce does not occur. Further detailsregarding re-bounce mitigation may be found in U.S. ProvisionalApplication No. 62/702,707, filed on Jul. 24, 2018, the entiredisclosure of which is incorporated by reference herein.

FIGS. 22A-23C illustrate examples of top-down views of an eyepiecehaving in-coupling optical elements configured to reduce re-bounce.In-coupling optical element 1022 a, 1022 b, 1022 c are configured toin-couple light such that it propagates in a propagation directiontowards the associated light distributing elements 730, 740, 750 (FIGS.22A-22C) or combined OPE/EPE's 1281, 1282, 1283 (FIGS. 23A-23C). Asillustrated, the in-coupling optical element 1022 a, 1022 b, 1022 c mayhave a shorter dimension along the propagation direction and a longerdimension along the transverse axis. For example, the in-couplingoptical element 1022 a, 1022 b, 1022 c may each be in the shape of arectangle with a shorter side along the axis of the propagationdirection and a longer side along an orthogonal axis. It will beappreciated that the in-coupling optical elements 1022 a, 1022 b, 1022 cmay have other shapes (for example, orthogonal, hexagonal, etc.). Inaddition, different ones of the in-coupling optical elements 1022 a,1022 b, 1022 c may have different shapes in some embodiments. Also,preferably, as illustrated, non-overlapping in-coupling optical elementsmay be positioned such that they are not in the propagation direction ofother in-coupling optical elements. For example, as shown in FIGS. 22A,22B, 23A, and 23B, the non-overlapping in-coupling optical elements maybe arranged in a line along an axis crossing (for example, orthogonalto) the axis of the propagation direction.

It will be appreciated that in the waveguide assemblies of FIGS. 22A-22Care similar, except for the overlap of the in-coupling optical elements1022 a, 1022 b, 1022 c. For example, FIG. 22A illustrates in-couplingoptical elements 1022 a, 1022 b, 1022 c with no overlap. FIG. 22Billustrates overlapping in-coupling optical elements 1022 a, 1022 c, andnon-overlapping in-coupling optical elements 1022 b. FIG. 22Cillustrates overlap between all the in-coupling optical elements 1022 a,1022 b, 1022 c.

The waveguide assemblies of FIGS. 23A-23C are also similar, except forthe overlap of the in-coupling optical elements 1022 a, 1022 b, 1022 c.FIG. 23A illustrates in-coupling optical elements 1022 a, 1022 b, 1022 cwith no overlap. FIG. 23B illustrates overlapping in-coupling opticalelements 1022 a, 1022 c, and non-overlapping in-coupling opticalelements 1022 b. FIG. 22C illustrates overlap between all thein-coupling optical elements 1022 a, 1022 b, 1022 c.

With reference now to FIG. 24A, it will be appreciated that the nanowireLED micro-displays have high etendue, which presents a challenge forefficient light utilization. As discussed herein, the nanowire LEDmicro-displays may include a plurality of individual light emitters.Each of these light emitters may have a large angular emission profile,for example, a Lambertian or near-Lambertian emission profile.Undesirably, not all of this light may be captured and directed to theeyepiece of the display system.

Advantageously, as discussed herein, nanowire LEDs may have an angularemission profile which is narrower than the angular emission profile ofplanar LEDs, for example, due to a periodic array structure that behavesas a photonic crystal material. Thus, the nanowire LEDs may have lightoutput with higher directionality in comparison to typical planarmicro-LEDs. In some embodiments, the directionality may be independentof pixel pitch and may be tailored by adjusting nanowire micro-LEDparameters, such as, but not limited to, nanowire material, dopant,dimensions, refractive indices, etc. As a result, as discussed herein,nanowire LED micro-displays may advantageously omit optics for steeringlight emitted from the nanowire LEDs. The lack of such optics may haveadvantages for simplifying display systems and also increasing lightoutput, as discussed herein. Nonetheless, in some embodiments, it may bedesirable to further manipulate the angular emission profile and/ordirection of the outputted light.

In some embodiments, various optical structures may be utilized tofurther narrow the angular spread of light emitted by the nanowire LEDs.FIG. 24A illustrates, in exaggerated form, an example of angularemission profiles of light emitted by individual light emitters 1044 ofa nanowire LED micro-display 1032, and light captured by projectionoptics 1070. The illustrated nanowire LED micro-display 1032 maycorrespond to any of the emissive-micro-displays disclosed herein,including the nanowire LED micro-displays 1032 a, 1032 b, 1032 c. Asillustrated, the projection optics 1070 may be sized such that it willcapture light having an angular emission profile 1046. However, theangular emission profiles 1046 in the light emitters 1044 may besignificantly larger; not all of the light emitted by the light emitters1044 may be incident on the projection optics 1070, nor necessarilyincident at angles at which the light may propagate into and through theprojection optics 1070. As a result, some of the light emitted by thelight emitter 1044 may undesirably be “wasted” since it is not capturedand ultimately relayed to the user's eye to form images. This may resultin images that appear darker than would be expected if more of the lightoutputted by the light emitters 1040 ultimately reached the user's eye.

In some embodiments, one strategy for capturing more of the lightemitted by the light emitters 1040 is to increase the size of theprojection optics 1070, to increase the size of the numerical apertureof the projection optics 1070 capturing light. In addition oralternatively, the projection optics 1070 may also be formed with highrefractive index materials (for example, having refractive indices above1.5) which may also facilitate light collection. In some embodiments,the projection optics 1070 may utilize a lens sized to capture adesired, high proportion of the light emitted by the light emitters1044. In some embodiments, the projection optics 1070 may be configuredto have an elongated exit pupil, for example, to emit light beams havinga cross-sectional profile similar to the shapes of the in-couplingoptical elements 1022 a, 1022 b, 1022 c of FIGS. 22A-23C. For example,the projection optics 1070 may be elongated in a dimension correspondingto the elongated dimension of the in-coupling optical elements 1022 a,1022 b, 1022 c of FIGS. 22A-23C. Without being limited by theory, suchelongated in-coupling optical elements 1022 a, 1022 b, 1022 c mayimprove the etendue mismatch between the nanowire LED micro-display andthe eyepiece 1020 (FIGS. 22A-23C). In some embodiments, the thickness ofthe waveguides of the eyepiece 1020 (for example, FIGS. 11A, and 12-23C)may be selected to increase the percentage of light effectivelycaptured, for example, by reducing re-bounce by increasing the re-bouncespacing, as discussed herein.

In some embodiments, one or more light collimators may be utilized toreduce or narrow the angular emission profile of light from the lightemitters 1044. As a result, more of the light emitted by the lightemitters 1044 may be captured by the projection optics 1070 and relayedto the eyes of a user, advantageously increasing the brightness ofimages and the efficiency of the display system. In some embodiments,the light collimators may allow the light collection efficiency of theprojection optics (the percentage of light emitted by the light emitters1044 that is captured by the projection optics) to reach values of 80%or more, 85% or more, or 90% or more, including about 85-95% or 85-90%.In addition, the angular emission profile of the light from the lightemitters 1044 may be reduced to 50° or less, 40° or less, or 30° orless. In some embodiments, the reduced angular emission profiles may bein the range of about 30-60°, 30-50°, or 30-40°. It will be appreciatedthat light from the light emitters 1044 may make out the shape of acone, with the light emitter 1044 at the vertex of the cone. The angularmission profile refers to the angle made out by the sides of the cone,with the associated light emitter 1044 at the vertex of the angle (asseen in a cross-section taken along a plane extending through the middleof the cone and including the cone apex).

FIG. 24B illustrates an example of the narrowing of angular emissionprofiles using an array of light collimators. As illustrated, thenanowire LED micro-display 1032 includes an array of light emitters1044, which emit light with an angular emission profile 1046. An array1300 of light collimators 1302 is disposed forward of the light emitters1044. In some embodiments, each light emitter 1044 is matched 1-to-1with an associated light collimator 1302 (one light collimator 1302 perlight emitter 1044). Each light collimator 1302 redirects incident lightfrom the associated light emitter 1044 to provide a narrowed angularemission profiles 1047. Thus, the relatively large angular emissionprofiles 1046 are narrowed to the smaller angular emission profiles1047.

In some embodiments, the light collimators 1302 and array 1300 may bepart of the light redirecting structures 1080 a, 180 c of FIGS. 12 and13A. Thus, light collimators 1302 may narrow the angular emissionprofile of the light emitters 1044 and also redirect the light such thatit propagates into the optical combiner 1050 at the appropriate anglesto define multiple light paths and the related multiple exit pupils. Itwill be appreciated that light may be redirected in particulardirections by appropriately shaping the light collimators 1302.

Preferably, the light collimators 1302 are positioned in tight proximityto the light emitters 1044 to capture a large proportion of the lightoutputted by the light emitters 1044. In some embodiments, there may bea gap between the light collimators 1302 and the light emitters 1044. Insome other embodiments, the light collimator 1302 may be in contact withthe light emitters 1044. It will be appreciated that the angularemission profile 1046 may make out a wide cone of light. Preferably, theentirety or majority of a cone of light from a light emitter 1044 isincident on a single associated light collimator 1302. Thus, in someembodiments, each light emitter 1044 is smaller (occupies a smallerarea) than the light receiving face of an associated light collimator1302. In some embodiments, each light emitter 1044 has a smaller widththan the spacing between neighboring far light emitters 1044.

Advantageously, the light collimators 1302 may increase the efficiencyof the utilization of light and may also reduce the occurrence ofcrosstalk between neighboring light emitters 1044. It will beappreciated that crosstalk between light emitters 1044 may occur whenlight from a neighboring light emitter is captured by a light collimator1302 not associated with that neighboring light emitter. That capturedlight may be propagated to the user's eye, thereby providing erroneousimage information for a given pixel.

With reference to FIGS. 24A and 24B, the size of the beam of lightcaptured by the projection optics 1070 may influence the size of thebeam of light which exits the projection optics 1070. As shown in FIG.24A, without the use light collimators, the exit beam may have arelatively large width 1050. As shown in FIG. 24B, with lightcollimators 1302, the exit beam may have a smaller width 1052. Thus, insome embodiments, the light collimators 1302 may be used to provide adesired beam size for in-coupling into an eyepiece. For example, theamount that the light collimators 1302 narrow the angular emissionprofile 1046 may be selected based at least partly upon the size of theintra-coupling optical elements in the eyepiece to which the lightoutputted by the projection optics 1070 is directed.

It will be appreciated that the light collimators 1302 may take variousforms. For example, the light collimators 1302 may be micro-lenses orlenslets, in some embodiments. As discussed herein, each micro-lenspreferably has a width greater than the width of an associated lightemitter 1044. The micro-lenses may be formed of curved transparentmaterial, such as glass or polymers, including photoresist and resinssuch as epoxy. In some embodiments, light collimators 1302 may benano-lenses, for example, diffractive optical gratings. In someembodiments, light collimators 1302 may be metasurfaces and/or liquidcrystal gratings. In some embodiments, light collimator's 1302 may takethe form of reflective wells.

It will be appreciated that different light collimators 1302 may havedifferent dimensions and/or shapes depending upon the wavelengths orcolors of light emitted by the associated light emitter 1044. Thus, forfull-color nanowire LED micro-displays, the array 1300 may include aplurality of light collimators 1302 with different dimensions and/orshapes depending upon the color of light emitted by the associate lightemitter 1044. In embodiments where the nanowire LED micro-display is amonochrome micro-display, the array 1300 may be simplified, with each ofthe light collimators 1302 in the array being configured to redirectlight of the same color. With such monochrome micro-displays, the lightcollimator 1302 may be similar across the array 1300 in someembodiments.

With continued reference to FIG. 24B, as discussed herein, the lightcollimators 1302 may have a 1-to-1 association with the light emitters1044. For example, each light emitter 1044 may have a discreteassociated light collimator 1302. In some other embodiments, lightcollimators 1302 may be elongated such that they extend across multiplelight emitters 1044. For example, in some embodiments, the lightcollimator 1302 may be elongated into the page and extend in front of arow of multiple light emitters 1044. In some other embodiments, a singlelight collimator 1302 may extend across a column of light emitters 1044.In yet other embodiments, the light collimator 1302 may include stackedcolumns and/or rows of lens structures (for example, nano-lensstructures, micro-lens structures, etc.).

As noted above, the light collimators 1302 may take the form ofreflective wells. FIG. 25A illustrates an example of a side view of anarray of tapered reflective wells for directing light to projectionoptics. As illustrated, the light collimator array 1300 may include asubstrate 1301 in which a plurality of light collimators 1302, in theform of reflective wells, may be formed. Each well may include at leastone light emitter 1044, which may emit light with a Lambertian angularemission profile 1046. The reflective walls 1303 of the wells of thelight collimators 1302 are tapered and reflect the emitted light suchthat it is outputted from the well with a narrower angular emissionprofile 1047. As illustrated, reflective walls 1303 may be tapered suchthat the cross-sectional size increases with distance from the lightemitter 1044. In some embodiments, the reflective walls 1303 may becurved. For example, the sides 1303 may have the shape of a compoundparabolic concentrator (CPC).

With reference now to FIG. 25B, an example of a side view of anasymmetric tapered reflective well is illustrated. As discussed herein,for example, as illustrated in FIGS. 12 and 13A, it may be desirable toutilize the light collimators 1302 to steer light in a particulardirection not normal to the surface of the light emitter 1044. In someembodiments, as viewed in a side view such as illustrated in FIG. 25B,the light collimator 1302 may be asymmetric, with the upper side 1303 aforming a different angle (for example, a larger angle) with the surfaceof the light emitter 1044 than the lower side 1303 b; for example, theangles of the reflective walls 1303 a, 1303 b relative to the lightemitter 1044 may differ on different sides of the light collimators 1302in order to direct the light in the particular non-normal direction.Thus, as illustrated, light exiting the light collimator 1302 maypropagate generally in a direction 1048 which is not normal to thesurface of the light emitter 1044. In some other embodiments, in orderto direct light in the direction 1048, the taper of the upper side 1303a may be different than the taper of the lower side; for example, theupper side 1303 a may flare out to a greater extent than the lower side1303 b.

With continued reference to FIG. 25B, the substrate 1301 may be formedof various materials having sufficient mechanical integrity to maintainthe desired shape of the reflective walls 1303. Examples of suitablematerials include metals, plastics, and glasses. In some embodiments,the substrate 1301 may be a plate of material. In some embodiments,substrate 1301 is a continuous, unitary piece of material. In some otherembodiments, the substrate 1301 may be formed by joining together two ormore pieces of material.

The reflective walls 1303 may be formed in the substrate 1301 by variousmethods. For example, the walls 1303 may be formed in a desired shape bymachining the substrate 1301, or otherwise removing material to definethe walls 1303. In some other embodiments, the walls 1303 may be formedas the substrate 1301 is formed. For example, the walls 1303 may bemolded into the substrate 1301 as the substrate 1301 is molded into itsdesired shape. In some other embodiments, the walls 1303 may be definedby rearrangement of material after formation of the body 2200. Forexample, the walls 1303 may be defined by imprinting.

Once the contours of the walls 1303 are formed, they may undergo furtherprocessing to form surfaces having the desired degree of reflection. Insome embodiments, the surface of the substrate 1301 may itself bereflective, for example, where the body is formed of a reflective metal.In such cases, the further processing may include smoothing or polishingthe interior surfaces of the walls 1303 to increase their reflectivity.In some other embodiments, the interior surfaces of the reflectors 2110may be lined with a reflective coating, for example, by a vapordeposition process. For example, the reflective layer may be formed byphysical vapor deposition (PVD) or chemical vapor deposition (CVD).

It will be appreciated that the location of a light emitter relative toan associated light collimator may influence the direction of emittedlight out of the light collimator. This is illustrated, for example, inFIGS. 26A-26C, which illustrate examples of differences in light pathsfor light emitters at different positions relative to center lines ofoverlying, associated light collimators. As shown in FIG. 26A, thenanowire LED micro-display another 30 has a plurality of light emitters1044 a, each having an associated light collimator 1302 whichfacilitates the output of light having narrowed angular emissionprofiles 1047. The light passes through the projection optics 1070(represented as a simple lens for ease of illustration), which convergesthe light from the various light emitters 1044 a onto an area 1402 a.

With continued reference to FIG. 26A, in some embodiments, each of thelight collimators 1302 may be symmetric and may have a center line whichextends along the axis of symmetry of the light collimator. In theillustrated configuration, the light emitters 1044 a are disposed on thecenter line of each of the light collimators 1302.

With reference now to FIG. 26B, light emitters 1044 b are offset by adistance 1400 from the center lines of their respective lightcollimators 1302. This offset causes light from the light emitters 1044b to take a different path through the light collimators 1302, whichoutput light from the light emitters 1044 b with narrowed angularemission profiles 1047 b. The projection optics 1070 then converges thelight from the light emitters 1044 b onto the area 1402 b, which isoffset relative to the area 1402 a on which light from the lightemitters 1044 a converge.

With reference now to FIG. 26C, light emitters 1044 c offset from boththe light emitters 1044 a and 1044 b are illustrated. This offset causeslight from the light emitters 1044 c to take a different path throughthe light collimators 1302 than light from the light emitters 1044 a and1044 b. This causes the light collimators 1302 to output light from thelight emitters 1044 c with narrowed angular emission profiles that takea different path to the projection optics 1070 than the light from thelight emitters 1044 a and 1044 b. Ultimately, the projection optics 1070converges the light from the light emitters 1044 c onto the area 1402 c,which is offset relative to the areas 1402 a and 1402 b.

With reference to FIGS. 26A-26C, each triad of light emitters 1044 a,1044 b, 1044 c may share a common light collimator 1302. In someembodiments, the micro-display 1030 may be a full-color micro-displayand each light emitter 1044 a, 1044 b, 1044 c may be configured to emitlight of a different component color. Advantageously, the offset areas1402 a, 1402 b, 1402 c may correspond to the in-coupling opticalelements of a waveguide in some embodiments. For example, the areas 1402a, 1402 b, 1402 c may correspond to the in-coupling optical element 1022a, 1022 b, 1022 c, respectively, of FIGS. 11A and 12. Thus, the lightcollimators 1302 and the offset orientations of the light emitters 1044a, 1044 b, 1044 c may provide an advantageously simple three-pupilprojection system 1010 using a full-color nanowire LED micro-display.

As noted herein, the light collimator 1302 may also take the form of anano-lens. FIG. 27 illustrates an example of a side view of individuallight emitters 1044 of a nanowire LED micro-display 1030 with anoverlying array 1300 of light collimators 1302 which are nano-lenses. Asdiscussed herein, individual ones of the light emitters 1044 may eachhave an associated light collimator 1302. The light collimators 1302redirect light from the light emitters 1044 to narrow the large angularemission profile 1046 of the light emitters 1044, to output light withthe narrowed angular emission profile 1047.

With continued reference to FIG. 27, in some embodiments, the lightcollimators 1302 may be grating structures. In some embodiments, thelight collimators 1302 may be gratings formed by alternating elongateddiscrete expanses (for example, lines) of material having differentrefractive indices. For example, expanses of material 1306 may beelongated into and out of the page and may be formed in and separated bymaterial of the substrate 1308. In some embodiments, the elongatedexpanses of material 1306 may have subwavelength widths and pitch (forexample, widths and pitch that are smaller than the wavelengths of lightthat the light collimators 1302 are configured to receive from theassociated light emitters 1044). In some embodiments, the pitch 1304 maybe 30-300 nm, the depth of the grating may be 10-1000 nm, the refractiveindex of the material forming the substrate 1308 may be 1.5-3.5, and therefractive index of the material forming the grating features 1306 maybe 1.5-2.5 (and different from the refractive index of the materialforming the substrate 1308).

The illustrated grating structure may be formed by various methods. Forexample, the substrate 1308 may be etched or nano-imprinted to definetrenches, and the trenches may be filled with material of a differentrefractive index from the substrate 1308 to form the grating features1306.

Advantageously, nano-lens arrays may provide various benefits. Forexample, the light collection efficiencies of the nano-lenslets may belarge, for example, 80-95%, including 85-90%, with excellent reductionsin angular emission profiles, for example, reductions to 30-40° (from180°). In addition, low levels of cross-talk may be achieved, since eachof the nano-lens light collimators 1302 may have physical dimensions andproperties (for example, pitch, depth, the refractive indices ofmaterials forming the feature 1306 and substrate 1308) selected to acton light of particular colors and possibly particular angles ofincidence, while preferably providing high extinction ratios (forwavelengths of light of other colors). In addition, the nano-lens arraysmay have flat profiles (for example, be formed on a flat substrate),which may facilitates integration with micro-displays that may be flatpanels, and may also facilitate manufacturing and provide highreproducibility and precision in forming the nano-lens array. Forexample, highly reproducible trench formation and deposition processesmay be used to form each nano-lens. Moreover, these processes allow,with greater ease and reproducibility, for variations betweennano-lenses of an array than are typically achieved when forming curvedlens with similar variations.

With reference now to FIG. 28, a perspective view of an example of ananowire LED micro-display 1030 is illustrated. It will be appreciatedthat the light collimator arrays 1300 advantageously allow light emittedfrom a micro-display to be routed as desired. As result, in someembodiments, the light emitters of a full-color micro-display may beorganized as desired, for example, for ease of manufacturing orimplementation in the display device. In some embodiments, the lightemitters 1044 may be arranged in rows or columns 1306 a, 1306 b, 1306 c.Each row or column may include light emitters 1044 configured to emitlight of the same component color. In displays where three componentcolors are utilized, there may be groups of three rows or columns whichrepeat across the micro-display 1030. It will be appreciated that wheremore component colors are utilized, each repeating group may have thatnumber of rows or columns. For example, where four component colors areutilized, each group may have four rows or four columns, with one row orone column formed by light emitters configured to emit light of a singlecomponent color.

In some embodiments, some rows or columns may be repeated to increasethe number of light emitters of a particular component color. Forexample, light emitters of some component colors may occupy multiplerows or columns. This may facilitate color balancing and/or may beutilized to address differential aging or reductions in light emissionintensity over time.

With continued reference to FIG. 28, each light emitter 1044 may beelongated along a particular axis (for example, along the y-axis asillustrated); that is, each light emitter has a length along theparticular axis, the length being longer than a width of the lightemitter. In addition, a set of light emitters configured to emit lightof the same component color may be arranged in a line 1306 a, 1306 b, or1306 c (for example a row or column) extending along an axis (forexample, the x-axis) which crosses (for example, is orthogonal to) thelight emitter 1044's elongate axis. Thus, in some embodiments, lightemitters 1044 of the same component color form a line 1306 a, 1306 b, or1306 c of light emitters, with the line extending along a first axis(for example, the x-axis), and with individual light emitters 1044within the line elongated along a second axis (for example, the y-axis).

In contrast, it will be appreciated that full-color micro-displaytypically include sub-pixels of each component color, with thesub-pixels arranged in particular relatively closely-packed spatialorientations in groups, with these groups reproduced across an array.Each group of sub-pixels may form a pixel in an image. In some cases,the sub-pixels are elongated along an axis, and rows or columns ofsub-pixels of the same component color extent along that same axis. Itwill be appreciated that such an arrangement allows the sub-pixels ofeach group to be located close together, which may have benefits forimage quality and pixel density. In the illustrated arrangement of FIG.28, however, sub-pixels of different component colors are relatively farapart, due to the elongate shape of the light emitters 1044; that is,the light emitters of the line 1306 a are relatively far apart from thelight emitters of the line 1306 c since the elongated shape of the lightemitters of the line 1306 b causes the light emitters 1306 a and 1306 cto be spaced out more than neighboring light emitters of a given line oflight emitters. While this may be expected to provide unacceptably poorimage quality if the image formed on the surface of the micro-display1030 was directly relayed to a user's eye, the use of the lightcollimator array 1300 advantageously allows light of different colors tobe routed as desired to form a high quality image. For example, light ofeach component color may be used to form separate monochrome imageswhich are then routed to and combined in an eyepiece, such as theeyepiece 1020 (for example, FIGS. 11A and 12-14).

With reference to FIGS. 27 and 28, in some embodiments, the lightemitters 1044 may each have an associated light collimator 1302. In someother embodiments, each line 1306 a, 1306 b, 1306 c of multiple lightemitters 1044 may have a single associated light collimator 1302. Thatsingle associated light collimator 1302 may extend across substantiallythe entirety of the associated line 1306 a, 1306 b, or 1306 c. In someother embodiments, the associated light collimator 1302 may be elongatedand extend over a plurality of light emitters 1044 forming a portion ofan associated line 1306 a, 1306 b, or 1306 c, and multiple similar lightcollimators 1302 may be provided along each of the associated lines 1306a, 1306 b, 1306 c.

It will be appreciated that the light collimators 1302 may be utilizedto direct light along different light paths to form multi-pupilprojections systems. For example, the light collimators 1302 may directlight of different component colors to two or three areas, respectively,for light in-coupling.

FIG. 29 illustrates an example of a wearable display system with thefull-color nanowire LED micro-display 1030 of FIG. 28 used to form amulti-pupil projection system 1010. In the illustrated embodiment, thefull-color nanowire LED micro-display 1030 emits light of threecomponent colors and forms a three-pupil projection system 1010. Theprojection system 1010 has three exit pupils through which image light1032 a, 1032 b, 1032 c of different component colors propagates to threelaterally-shifted light in-coupling optical elements 1022 a, 1022 b,1022 c, respectively, of an eyepiece 1020. The eyepiece 1020 then relaysthe image light 1032 a, 1032 b, 1032 c to the eye 210 of a user.

The emissive-micro-display 1030 includes an array of light emitters1044, which may be subdivided into monochrome light emitters 1044 a,1044 b, 1044 c, which emit the image light 1032 a, 1032 b, 1032 c,respectively. It will be appreciated that the light emitters 1044 emitimage light with a broad angular emission profile 1046. The image lightpropagates through the array 1300 of light collimators, which reducesthe angular emission profile to the narrowed angular emission profile1047.

In addition, the array of 1300 of light collimators is configured toredirect the image light (image light 1032 a, 1032 b, 1032 c) such thatthe image light is incident on the projection optics 1070 at angleswhich cause the projection optics 1070 to output the image light suchthat the image light propagates to the appropriate in-coupling opticalelement 1022 a, 1022 b, 1022 c. For example, the 1300 array of lightcollimators is preferably configured to: direct the image light 1032 asuch that it propagates through the projection optics 1070 and isincident on the in-coupling optical element 1022 a; direct the imagelight 1032 b such that it propagates through the projection optics 1070and is incident on the in-coupling optical element 1022 b; and directthe image light 1032 c such that it propagates through the projectionoptics 1070 and is incident on the in-coupling optical element 1022 c.

Since different light emitters 1044 may emit light of differentwavelengths and may need to be redirected into different directions toreach the appropriate in-coupling optical element, in some embodiments,the light collimators associated with different light emitters 1044 mayhave different physical parameters (for example, different pitches,different widths, etc.). Advantageously, the use of flat nano-lenses aslight collimators facilitates the formation of light collimators whichvary in physical properties across the array 1300 of light collimators.As noted herein, the nano-lenses may be formed using patterning anddeposition processes, which facilitates the formation of structures withdifferent pitches, widths, etc. across a substrate.

With reference again to FIG. 24A, it will be appreciated that theillustrated display system shows a single nanowire LED micro-display andomits an optical combiner 1050 (FIGS. 11A and 12-13B). In embodimentsutilizing an optical combiner 1050, the reflective surfaces 1052, 1054(FIGS. 11A, 12-13B, and 30B) in the optical combiner 1050 are preferablyspecular reflectors, and light from the light emitters 1044 would beexpected to retain their large angular emission profiles after beingreflected from the reflective surfaces 1052, 1054. Thus, the problemswith wasted light shown in FIG. 24A are similarly present when anoptical combiner 1050 is utilized.

With reference now to FIG. 30A, an example of a wearable display systemwith a nanowire LED micro-display and an associated array of lightcollimators is illustrated. FIG. 30A shows additional details regardingthe interplay between the light emitters 1044, the light collimators1302, and the in-coupling optical elements of the eyepiece 1020. Thedisplay system includes a micro-display 1030 b, which may be afull-color micro-display in some embodiments. In some other embodiments,the micro-display 1030 b may be a monochrome micro-display andadditional monochrome micro-displays (not shown) may be provided atdifferent faces of the optional optical combiner 1050 (as shown in FIG.30C).

With continued reference to FIG. 30A, the micro-display 1030 b includesan array of light emitters 1044, each of which emits light with a wideangular emission profile (for example, a Lambertian angular emissionprofile). Each light emitter 1044 has an associated, dedicated lightcollimator 1302 which effectively narrows the angular emission profileto a narrowed angular remission profile 1047. Light beams 1032 b withthe narrowed angular emission profiles pass through the projectionoptics 1070, which projects or converges those light beams onto thein-coupling optical element 1022 b. It will be appreciated that thelight beams 1032 b have a certain cross-sectional shape and size 1047 a.In some embodiments, the in-coupling optical element 1022 b has a sizeand shape which substantially matches or is larger than thecross-sectional shape and size of the light beam 1032 b, when that beam1032 b is incident on that in-coupling optical element 1022 b. Thus, insome embodiments, the size and shape of the in-coupling optical element1022 b may be selected based upon the cross-sectional size and shape ofthe light beam 1032 b when incident on the in-coupling optical element1022 b. In some other embodiments, other factors (re-bounce mitigation,or the angles or field of view supported by the in-coupling opticalelements 1022 b) may be utilized to determine the size and shape of thein-coupling optical element 1022 b, and the light collimator 1302 may beconfigured (for example, sized and shaped) to provide the light beam1032 b with an appropriately sized and shaped cross-section, which ispreferably fully or nearly fully encompassed by the size and shape ofthe in-coupling optical element 1022 b. In some embodiments, physicalparameters for the light collimator 1302 and the in-coupling opticalelement 1022 b may be mutually modified to provide highly efficientlight utilization in conjunction with other desired functionality (forexample, re-bounce mitigation, support for the desired fields of view,etc.). Advantageously, the above-noted light collimation provided by thelight collimator 1302, and matching of the cross-sectional size andshape of the light beam 1032 b with the size and shape of thein-coupling optical element 1022 b allows the in-coupling opticalelement 1022 b to capture a large percentage of the incident light beam1032 b. The in-coupled light then propagates through the waveguide 1020b and is out-coupled to the eye 210.

In some embodiments, the light collimators 1302 are micro-lensesdisposed directly on and surrounding associated light emitters 1044. Insome embodiments, neighboring micro-lenses 1302 nearly contact ordirectly contact one another. It will be appreciated that light from thelight emitters 1044 may fill the associated micro-lens 1302, effectivelymagnifying the area encompassed by the light emitter 1044.Advantageously, such a configuration reduces the perceptibility of theareas which do not emit light and may otherwise be visible as darkspaces to a user. However, because micro-lens 1302 effectively magnifiesthe associated light emitter 1044 such that it extends across the entirearea of the micro-lens 1302, the areas which do not emit light may bemasked.

With continued reference to FIG. 30A, the relative sizes of the lightemitters 1044 and light collimators 1302 may be selected such that lightfrom the light emitters 1044 fills the associated light collimators1302. For example, the light emitters 1044 may be spaced sufficientlyfar apart such that micro-lens collimators 1302 having the desiredcurvature may be formed extending over individual ones of the lightemitters 1044. In addition, as noted above, the size and shape of theintra-coupling optical element 1022 b is preferably selected such thatit matches or exceeds the cross-sectional shape and size of the lightbeam 1032 b when incident on that in-coupling optical element 1022 b.Consequently, in some embodiments, a width 1025 of the in-couplingoptical element 1022 b is equal to or greater than the width of themicro-lens 1302. Preferably, the width 1025 is greater than the width ofthe micro-lens 1302 to account for some spread in the light beam 1032 b.As discussed herein, the width 1025 may also be selected to mitigaterebounce and may be shorter than the length (which is orthogonal to thewidth) of the in-coupling optical element 1022 b. In some embodiments,the width 1025 may extend along the same axis as the direction ofpropagation of incoupled light 1032 b through the waveguide 1020 bbefore being out-coupled for propagation to the eye 210.

With reference now to FIG. 30B, an example of a light projection system1010 with multiple nanowire LED micro-displays 1030 a, 1030 b, 1030 c,and associated arrays 1300 a, 1300 b, 1300 c of light collimators,respectively, is illustrated. The angular emission profiles of lightemitted by the micro-displays 1030 a, 1030 b, 1030 c are narrowed by thelight collimator arrays 1300 a, 1300 b, 1300 c, thereby facilitating thecollection of a large percentage of the emitted light by the projectionoptics 1070 after the light propagates through the optical combiner1050. The projection optics 1070 then directs the light to an eyepiecesuch as the eyepiece 1020 (for example, FIGS. 11A and 12-14) (notshown).

FIG. 30C illustrates an example of a wearable display system withmultiple nanowire LED micro-displays 1030 a, 1030 b, 1030 c, each withan associated array 1300 a, 1300 b, 1300 c, respectively, of lightcollimators. The illustrated display system includes a plurality ofmicro-displays 1030 a, 1030 b, 1030 c for emitting light with imageinformation. As illustrated, the micro-displays 1030 a, 1030 b, 1030 cmay be micro-LED panels. In some embodiments, the micro-displays may bemonochrome micro-LED panels, each configured to emit a differentcomponent color. For example, the micro-display 1030 a may be configuredto emit light 1032 a which is red, the micro-display 1030 b may beconfigured to emit light 1032 b which is green, and the micro-display1030 c may be configured to emit light 1032 c which is blue.

Each micro-display 1030 a, 1030 b, 1030 c may have an associated array1300 a, 1300 b, 1300 c, respectively, of light collimators. The lightcollimators narrow the angular emission profile of light 1032 a, 1032 b,1032 c from light emitters of the associated micro-display. In someembodiments, individual light emitters have a dedicated associated lightcollimator (as shown in FIG. 30A).

With continued reference to FIG. 30C, the arrays 1300 a, 1300 b, 1300 cof light collimators are between the associated micro-displays 1030 a,1030 b, 1030 c and the optical combiner 1050, which may be an X-cube. Asillustrated, the optical combiner 1050 has internal reflective surfaces1052, 1054 for reflecting incident light out of an output face of theoptical combiner. In addition to narrowing the angular emission profileof incident light, the arrays 1300 a, 1300 c of light collimators may beconfigured to redirect light from associated micro-displays 1030 a, 1030c such that the light strikes the internal reflective surfaces 1052,1054 of the optical combiner 1050 at angles appropriate to propagatetowards the associated light in-coupling optical elements 1022 a, 1022c, respectively. In some embodiments, in order to redirect light in aparticular direction, the arrays 1300 a, 1300 c of light collimators mayinclude micro-lens or reflective wells, which may be asymmetrical and/orthe light emitters may be disposed off-center relative to the micro-lensor reflective wells, as disclosed herein.

With continued reference to FIG. 30C, projection optics 1070 (forexample, projection lens) is disposed at the output face of the opticalcombiner 1050 to receive image light exiting from that optical combiner.The projection optics 1070 may include lenses configured to converge orfocus image light onto the eyepiece 1020. As illustrated, the eyepiece1020 may include a plurality of waveguides, each of which is configuredto in-couple and out-couple light of a particular color. For example,waveguide 1020 a may be configured to receive red light 1032 a from themicro-display 1030 a, waveguide 1020 b may be configured to receivegreen light 1032 b from the micro-display 1030 b, and waveguide 1020 cmay be configured to receive blue light 1032 c from the micro-display1030 c. Each waveguide 1020 a, 1020 b, 1020 c has an associated lightin-coupling optical elements 1022 a, 1022 b, 1022 c, respectively, forin-coupling light therein. In addition, as discussed herein, thewaveguides 1020 a, 1020 b, 1020 c may correspond to the waveguides 670,680, 690, respectively, of FIG. 9B and may each have associatedorthogonal pupil expanders (OPE's) and exit pupil expanders (EPE's),which ultimately out-couple the light 1032 a, 1032 b, 1032 c to a user.

As discussed herein, the wearable display system incorporatingmicro-displays is preferably configured to output light with differentamounts of wavefront divergence, to provide comfortableaccommodation-vergence matching for the user. These different amounts ofwavefront divergence may be achieved using out-coupling optical elementswith different optical powers. As discussed herein, the out-couplingoptical elements may be present on or in waveguides of an eyepiece suchas the eyepiece 1020 (for example, FIGS. 11A and 12-14). In someembodiments, lenses may be utilized to augment the wavefront divergenceprovided by the out-couple optical elements or may be used to providethe desired wavefront divergence in configurations where the out-coupleoptical elements are configured to output collimated light.

FIGS. 31A and 31B illustrate examples of eyepieces 1020 having lens forvarying the wavefront divergence of light to a viewer. FIG. 31Aillustrates an eyepiece 1020 having a waveguide structure 1032. In someembodiments, as discussed herein, light of all component colors may bein-coupled into a single waveguide, such that the waveguide structure1032 includes only the single waveguide. This advantageously providesfor a compact eyepiece. In some other embodiments, the waveguidestructure 1032 may be understood to include a plurality of waveguides(for example, the waveguides 1032 a, 1032 b, 1032 c of FIGS. 11A and12-13A), each of which may be configured to relay light of a singlecomponent color to a user's eye.

In some embodiments, the variable focus lens elements 1530, 1540 may bedisposed on either side of the waveguide structure 1032. The variablefocus lens elements 1530, 1540 may be in the path of image light fromthe waveguide structure 1032 to the eye 210, and also in the path oflight from the ambient environment through the waveguide structure 10032 to the eye 210. The variable focus optical element 1530 may modulatethe wavefront divergence of image light outputted by the waveguidestructure 1032 to the eye 210. It will be appreciated that the variablefocus optical element 1530 may have optical power which may distort theeye 210's view of the world. Consequently, in some embodiments, a secondvariable focus optical element 1540 may be provided on the world side ofthe waveguide structure 1032. The second variable focus optical element1540 may provide optical power opposite to that of the variable focusoptical element 1530 (or opposite to the net optical power of theoptical element 1530 and the waveguide structure 1032, where thewaveguide structure 1032 has optical power), so that the net opticalpower of the variable focus lens elements 1530, 1540 and the waveguidestructure 1032 is substantially zero.

Preferably, the optical power of the variable focus lens elements 1530,1540 may be dynamically altered, for example, by applying an electricalsignal thereto. In some embodiments, the variable focus lens elements1530, 1540 may include a transmissive optical element such as a dynamiclens (for example, a liquid crystal lens, an electro-active lens, aconventional refractive lens with moving elements, amechanical-deformation-based lens, an electrowetting lens, anelastomeric lens, or a plurality of fluids with different refractiveindices). By altering the variable focus lens elements' shape,refractive index, or other characteristics, the wavefront of incidentlight may be changed. In some embodiments, the variable focus lenselements 1530, 1540 may include a layer of liquid crystal sandwichedbetween two substrates. The substrates may include an opticallytransmissive material such as glass, plastic, acrylic, etc.

In some embodiments, in addition or as alternative to providing variableamounts of wavefront divergence for placing virtual content on differentdepth planes, the variable focus lens elements 1530, 1540 and waveguidestructure 1032 may advantageously provide a net optical power equal tothe user's prescription optical power for corrective lenses. Thus, theeyepiece 1020 may serve as a substitute for lenses used to correct forrefractive errors, including myopia, hyperopia, presbyopia, andastigmatism. Further details regarding the use of variable focus lenselements as substitutes for corrective lenses may be found in U.S.application Ser. No. 15/481,255, filed Apr. 6, 2017, the entiredisclosure of which is incorporated by reference herein.

With reference now to FIG. 31B, in some embodiments, the eyepiece 1020may include static, rather than variable, lens elements. As with FIG.31B, the waveguide structure 1032 may include a single waveguide (forexample, which may relay light of different colors) or a plurality ofwaveguides (for example, each of which may relay light of a singlecomponent color). Similarly, the waveguide structure 1034 may include asingle waveguide (for example, which may relay light of differentcolors) or a plurality of waveguides (for example, each of which mayrelay light of a single component color). The one or both of thewaveguide structures 1032, 1034 may have optical power and may outputlight with particular amounts of wavefront divergence, or may simplyoutput collimated light.

With continued reference to FIG. 31B, the eyepiece 1020 may includestatic lens elements 1532, 1534, 1542 in some embodiments. Each of theselens elements are disposed in the path of light from the ambientenvironment through waveguide structures 1032, 1034 into the eye 210. Inaddition, the lens element 1532 is between a waveguide structure 1003 2and the eye 210. The lens element 1532 modifies a wavefront divergenceof light outputted by the waveguide structure 1032 to the eye 210.

The lens element 1534 modifies a wavefront divergence of light outputtedby the waveguide structure 1034 to the eye 210. It will be appreciatedthat the light from the waveguide structure 1034 also passes through thelens element 1532. Thus, the wavefront divergence of light outputted bythe waveguide structure 1034 is modified by both the lens element 1534and the lens element 1532 (and the waveguide structure 1032 in caseswhere the waveguide structure 1003 2 has optical power). In someembodiments, the lens elements 1532, 1534 and the waveguide structure1032 provide a particular net optical power for light outputted from thewaveguide structure 1034.

The illustrated embodiment provides two different levels of wavefrontdivergence, one for light outputted from the waveguide structure 1032and a second for light outputted by a waveguide structure 1034. As aresult, virtual objects may be placed on two different depth planes,corresponding to the different levels of wavefront divergence. In someembodiments, an additional level of wavefront divergence and, thus, anadditional depth plane may be provided by adding an additional waveguidestructure between lens element 1532 and the eye 210, with an additionallens element between the additional waveguide structure and the eye 210.Further levels of wavefront divergence may be similarly added, by addingfurther waveguide structures and lens elements.

With continued reference to FIG. 31B, it will be appreciated that thelens elements 1532, 1534 and the waveguide structures 1032, 1034 providea net optical power that may distort the users view of the world. As aresult, lens element 1542 may be used to counter the optical power anddistortion of ambient light. In some embodiments, the optical power ofthe lens element 1542 is set to negate the aggregate optical powerprovided by the lens elements 1532, 1534 and the waveguide structures1032, 1034. In some other embodiments, the net optical power of the lenselement 1542; the lens elements 1532, 1534; and the waveguide structures1032, 1034 is equal to a user's prescription optical power forcorrective lenses.

In some embodiments, and as illustrated in FIGS. 32A and 32B, even wheredifferent micro-displays are utilized to generate light of differentcomponent colors, an optical combiner may be omitted from the projectionsystem 1500. For example, the micro-displays 1030 a-1030 c may eachroute light via a dedicated associated one of the projection optics 1070a-1070 c to the eyepiece 1020. As illustrated, micro-display 1030 a hasan associated projection optics 1070 a which focuses light ontoassociated in-coupling optical elements 1022 a, micro-display 1030 b hasan associated projection optics 1070 b which focuses light ontoassociated in-coupling optical elements 1022 b, and micro-display 1030 chas an associated projection optics 1070 c which focuses light ontoassociated in-coupling optical elements 1022 c.

It will be appreciated that in embodiments in which an optical combiner1500 is not used, several example benefits may be achieved. As anexample, there may be improved light collection as the microdisplays1030 a-1030 c may be placed closer to the projection optics 1070 a-1070c when the intervening optical combiner 1500 is omitted. As a result,higher light utilization efficiency and image brightness may beachieved. In addition, optical aberrations (such as crosstalk) andinefficiencies (due to the requirements for a large acceptance angle andinefficiency in reflecting light) related to light propagation throughan X-cube may advantageously be avoided. As another example, theprojection system 1500 may be simplified and tailored to light of aparticular component color. For example, an optics design for eachrespective projection optics 1070 a-1070C may be calibrated separatelyfor light of each component color generated by the microdisplays 1030a-1030 c. In this way, the projection system 1500 may avoid the need forachromatization of the projection optics.

As another example benefit, and as illustrated in FIG. 32A, light fromeach of the projection optics 1070 a-1070 c may advantageously be morespecifically focused onto respective associated in-coupling opticalelements 1022 a-1022 c. The examples of FIGS. 32A-32B allow for moreprecise focusing of each component color onto a respective in-couplingelement 1022 a-1022 c. The projection optics 1070 a-1070 c for eachcomponent color may be configured to precisely focus light onto arespective in-coupling element 1022 a-1022 c. In some embodiments, thisprecise focusing may improve image quality by providing well-focusedimages of each component color.

FIG. 32A illustrates an example of a light projection system 1500without an optical combiner (for example, the optical combiner 1050described above). In the illustrated example, three microdisplays 1030a-1030 c provide light (for example, component color light) torespective projection optics 1070 a-1070 c. Light from each microdisplay1030 a 1030 c may be routed through the projection optics 1070 a-1070 cand focused onto respective in-coupling elements 1022 a-1022 c includedin the eyepiece 1020. It will be appreciated that each microdisplay 1030a-1030 c may be a distinct structure, with each micro-display includingan array of nano wire LEDs formed on a different backplane.

FIG. 32B illustrates another example of a wearable display system havinga light projection system without an optical combiner. In someembodiments, the microdisplays 1030 a-1030 c may form a single integralunit, for example, the microdisplays 1030 a-1030 c be placed on a singlebackplane 1093. In some embodiments, the backplane 1093 may be a siliconbackplane, which may include electrical components for the microdisplays1030 a-1030 c, and may include various electronic devices such as CMOSdevices for controlling the nanowire LEDs of the micro-displays 1030a-1030 c.

As discussed herein, with reference to both FIGS. 32A and 32B, it willbe appreciated that the illustrated eyepiece 1020 may be formed of asingle waveguide in some embodiments, rather than three waveguides. Insuch embodiments, the single waveguide may support in-coupling, internalpropagation, and out-coupling of a plurality of colors (for example twoor three colors). The single waveguide may include each of thein-coupling optical elements 1022 a, 1022 b, 1022 c in a differentlocation aligned with the light output of an associated respectivemicro-display 1030 a, 1030 b, 1030 c. As discussed herein, in someembodiments, the single waveguide may be formed of an opticallytransmissive, high refractive index material (for example, siliconcarbide).

Various example embodiments of the invention are described herein.Reference is made to these examples in a non-limiting sense. They areprovided to illustrate more broadly applicable aspects of the invention.Various changes may be made to the invention described and equivalentsmay be substituted without departing from the spirit and scope of theinvention.

For example, while advantageously utilized with AR displays that provideimages across multiple depth planes, the virtual content disclosedherein may also be displayed by systems that provide images on a singledepth plane. In addition, the display systems herein may also functionas virtual reality displays in which light from the ambient environmentis not transmitted through the eyepieces.

As another example, it will also be appreciated that each of theillustrated eyepieces 1020 with multiple waveguides may also simplyinclude only a single waveguide. In some embodiments, the singlewaveguide may be formed of an optically transmissive high refractiveindex material, for example silicon carbide (SiC). The single waveguidemay include a single in-coupling optical element to, for example, incouple light of multiple different component colors. In otherembodiments, the single waveguide may include multiple spatiallyseparated in-coupling optical elements, which may each be configured toin couple light of different component colors. In some otherembodiments, at least one of the in-coupling optical element may beconfigured to in couple light of multiple different component colors.

In addition, many modifications may be made to adapt a particularsituation, material, composition of matter, process, process act, orstep(s) to the objective(s), spirit, or scope of the present invention.Further, as will be appreciated by those with skill in the art that eachof the individual variations described and illustrated herein hasdiscrete components and features which may be readily separated from orcombined with the features of any of the other several embodimentswithout departing from the scope or spirit of the present inventions.All such modifications are intended to be within the scope of claimsassociated with this disclosure.

The invention includes methods that may be performed using the subjectdevices. The methods may include the act of providing such a suitabledevice. Such provision may be performed by the user. In other words, the“providing” act merely requires the user obtain, access, approach,position, set-up, activate, power-up or otherwise act to provide therequisite device in the subject method. Methods recited herein may becarried out in any order of the recited events that is logicallypossible, as well as in the recited order of events.

Example aspects of the invention, together with details regardingmaterial selection and manufacture have been set forth above. As forother details of the present invention, these may be appreciated inconnection with the above-referenced patents and publications as well asgenerally known or appreciated by those with skill in the art. The samemay hold true with respect to method-based aspects of the invention interms of additional acts as commonly or logically employed.

In addition, though the invention has been described in reference toseveral examples optionally incorporating various features, theinvention is not to be limited to that which is described or indicatedas contemplated with respect to each variation of the invention. Variouschanges may be made to the invention described and equivalents (whetherrecited herein or not included for the sake of some brevity) may besubstituted without departing from the spirit and scope of theinvention. In addition, where a range of values is provided, it isunderstood that every intervening value, between the upper and lowerlimit of that range and any other stated or intervening value in thatstated range, is encompassed within the invention.

Also, it is contemplated that any optional feature of the inventivevariations described may be set forth and claimed independently, or incombination with any one or more of the features described herein.Reference to a singular item, includes the possibility that there areplural of the same items present. More specifically, as used herein andin claims associated hereto, the singular forms “a,” “an,” “said,” and“the” include plural referents unless the specifically stated otherwise.In other words, use of the articles allow for “at least one” of thesubject item in the description above as well as claims associated withthis disclosure. It is further noted that such claims may be drafted toexclude any optional element. As such, this statement is intended toserve as antecedent basis for use of such exclusive terminology as“solely,” “only” and the like in connection with the recitation of claimelements, or use of a “negative” limitation. Without the use of suchexclusive terminology, the term “including” in claims associated withthis disclosure shall allow for the inclusion of any additionalelement—irrespective of whether a given number of elements areenumerated in such claims, or the addition of a feature could beregarded as transforming the nature of an element set forth in suchclaims.

Accordingly, the claims are not intended to be limited to theembodiments shown herein, but are to be accorded the widest scopeconsistent with this disclosure, the principles and the novel featuresdisclosed herein.

What is claimed is:
 1. A head-mounted display system comprising: ahead-mountable frame; a nanowire micro-LED display supported by theframe, wherein the nanowire LED micro-display is configured to outputimage light; and an eyepiece supported by the frame, wherein theeyepiece is configured to receive the image light from the nanowire LEDmicro-display and to direct the image light to an eye of a user uponmounting the frame on the user.
 2. The head-mounted display system ofclaim 1, wherein the nanowire LED micro-display is one of a plurality ofnanowire LED micro-displays, further comprising an X-cube prism, whereineach of the nanowire micro-LED displays faces a different side of theX-cube prism, wherein the eyepiece comprises an in-coupling opticalelement, and wherein an output side of the X-cube prism faces the lightin-coupling element.
 3. The head-mounted display system of claim 2,wherein the nanowire LED micro-displays are monochrome nanowire LEDmicro-displays.
 4. The head-mounted display system of claim 3, whereinreflective surfaces of the X-cube prism are configured to localize lightfrom different monochrome nanowire LED micro-displays onto differentareas of the eyepiece.
 5. The head-mounted display system of claim 4,wherein the eyepiece comprises a plurality of in-coupling opticalelements having a spatial arrangement providing distinct light pathsfrom the X-cube prism to the in-coupling optical elements, wherein aspatial arrangement of the areas corresponds to the spatial arrangementof the in-coupling optical elements.
 6. The head-mounted display systemof claim 1, wherein the eyepiece comprises a plurality of waveguidesforming a waveguide stack, each waveguide of the waveguide stackcomprising: an in-coupling optical element configured to in-couple lightfrom the nanowire LED micro-display into the waveguide; and anout-coupling optical element configured to out-couple in-coupled lightout of the waveguide.
 7. The head-mounted display system of claim 6,wherein the waveguide stack comprises a plurality of sets of waveguides,wherein each set of waveguides comprises a dedicated waveguide for acomponent color.
 8. The head-mounted display system of claim 1, furthercomprising variable focus lens elements, wherein a waveguide comprisingdiffractive light in-coupling and out-coupling optical elements isbetween first and second variable focus lens elements, wherein the firstvariable focus lens element is configured to modify a wavefrontdivergence of light outputted by the waveguide, wherein the secondvariable focus lens element is configured to modify a wavefrontdivergence of light from an external world propagating through thesecond variable focus lens element.
 9. The head-mounted display systemof claim 1, further comprising a color filter between two neighboringwaveguides of a waveguide stack of the eyepiece, wherein a first of theneighboring waveguides precedes a second of the neighboring waveguidesin a light path extending from the micro-display, wherein the colorfilter is configured to selectively absorb light of a wavelengthcorresponding to a wavelength of light configured to be in-coupled bythe in-coupling optical element of the first of the neighboringwaveguides.
 10. The head-mounted display system of claim 9, furthercomprising: a third waveguide following the second of the neighboringwaveguides in the light path; and an other color filter configured toselectively absorb light of a wavelength corresponding to a wavelengthof light configured to be in-coupled by the in-coupling optical elementof the second of the neighboring waveguides.
 11. The head-mounteddisplay system of claim 1, wherein the nanowire LED micro-displaycomprises spaced-apart arrays of monochrome nanowire micro-LEDs on acommon substrate backplane.
 12. The head-mounted display system of claim11, wherein the eyepiece comprises a plurality of waveguides, whereinthe waveguides form a waveguide stack, wherein each waveguide comprisesin-coupling optical elements, wherein, as seen in a top-down view, aspatial arrangement of the in-coupling optical elements comprisesdifferent in-coupling optical elements of different waveguides localizedin different spaced-apart positions, wherein a spatial arrangement ofthe arrays of monochrome nanowire micro-LEDs match a spatial arrangementof the in-coupling optical elements.
 13. The head-mounted display systemof claim 1, wherein the nanowire LED micro-display comprises an array ofnanowire micro-LEDs, wherein some of the nanowire micro-LEDs areconfigured to emit light of different component colors than others ofthe array of nanowire micro-LEDs.
 14. A head-mounted display systemcomprising: a waveguide assembly comprising one or more waveguides; andan image projection system comprising an array of nanowire micro-LEDs,the image projection system configured to project images onto thewaveguide assembly, wherein each waveguide of the waveguide assemblycomprises: an in-coupling optical element configured to incouple lightfrom the image projection system into the waveguide; and an out-couplingoptical element configured to outcouple incoupled light out of thewaveguide, wherein the waveguide assembly is configured to output theoutcoupled light with variable amounts of wavefront divergencecorresponding to a plurality of depth planes.
 15. The head-mounteddisplay system of claim 14, wherein the nanowire micro-LEDs each have anangular emission profile of less than 50°.
 16. The head-mounted displaysystem of claim 14, further comprising projection optics configured toconverge light from the nanowire LED micro-display onto the in-couplingoptical elements of the one or more waveguides.
 17. The head-mounteddisplay system of claim 14, wherein individual ones of the lightemitters are configured to emit light of one of a plurality of componentcolors, wherein the waveguide assembly comprises a plurality of sets ofwaveguides, wherein each set of waveguides comprises a dedicatedwaveguide for each component color, wherein each set of waveguidescomprises out-coupling optical elements configured to output light withwavefront divergence corresponding to a common depth plane, whereindifferent sets of waveguides output light with different amounts ofwavefront divergence corresponding to different depth planes.
 18. Thehead-mounted display system of claim 14, further comprising variablefocus lens elements, wherein the waveguide assembly is between first andsecond variable focus lens elements, wherein the first variable focuslens element is configured to modify a wavefront divergence of lightoutputted by the waveguide assembly, wherein the second variable focuslens element is configured to modify a wavefront divergence of lightfrom an external world to the second variable focus lens element. 19.The head-mounted display system of claim 14, further comprisingabsorptive color filters on major surfaces of at least some of thewaveguides, wherein the absorptive color filters on major surfaces ofthe waveguides are configured to absorb light of wavelengths in-coupledinto a corresponding waveguide, wherein the waveguides are arranged in astack.
 20. The head-mounted display system of claim 14, wherein thewaveguide assembly comprises a stack of waveguides, wherein thein-coupling optical elements are configured to in-couple light with thein-coupled light propagating generally in a propagation directionthrough an associated waveguide, wherein the in-coupling opticalelements occupy an area having a width parallel to the propagationdirection and a length along an axis crossing the propagation direction,wherein the length is greater than the width.